Late Swap
On DK the main slate of games consists of the Sunday 1PM and 4PM games in (EST). Once a game starts, players from that game are locked in the lineup and you cannot swap them out. However, players in the late game can be moved around. This is what a normal NFL Sunday slate looks like:

In my opinion, late swap is one of the biggest edges you can take advantage of in Reignmakers. Because of how awful the DK interface is, I find that most players use late swap inefficiently or just flat out do not use it.
Generally, for a slate of games you want to have a certain percentage of lineups that have between 1-4 players in the early and 1-4 in the late games. It's extremely rare that you will have 5-0 or 0-5 but it can happen. The exact ratio will depend on your confidence levels in the players in each window. Vegas lines for game totals can give you an idea of what games or who you want to target (usually games with higher lines).
You'll want to have between one and three 0-5 lineups so that you can evacuate your good late players from dud early lineups, start fresh, and shoot for a top 100 finish.
To late swap you will need to have dud players (backup or injured skill starters/defense/kickers) in the 4 o’clock games.
I’ve gone ahead and analyzed the NFL schedule in order to identify the teams with the greatest number of late games so that you can get the most bang for your buck with late swapping (note the NFL does have a flexible scheduling policy that allows them to move games around).

One thing I’ve also discovered is that if you have backups from the cowboys, chiefs, and eagles then you will have backups in the 4:25pm games for all weeks except for week 11.
Casual –
When you construct a lineup make sure that your latest skill position players are in the flex and the WR/TE slot. If you don’t you will lose a great deal of flexibility. Late swap will matter even more if you do deep roster as there are multiple asynchronous games (Typically Thursday -> Sunday 1PM -> 4PM -> 8PM -> Monday).
Baller -
Take advantage of duds to create more lineups with the same late-swap players. In the previous example we can use four duds (Davis and Thibodeaux + 2) to cheaply submit another lineup for which we might not have had another good RB and WR option. Swap McCaffrey and Aiyuk into the one which performs best in the early games. (You will need 2 more duds for the swap out for a total of 4).
Hobbyist/Diehard -
Late swapping is an art that is 80% preparation and 20% luck. What I like to do here is build “shells” that I take shots with so that I can late swap into later. For example, let’s say that the Dolphins versus the Chargers is in the 4PM games and that I think there's a high chance that Tua/Tyreek Hill/Keenan Allen stack will be the nuts (highest possible scoring). I should then try to “guess” the other two spots in the nut lineup and take chances on those in the early games. I'll want to build unlikely RB/WR and WR/WR shells and if one or two hit really hard I can then swap that stack into that lineup.
This is something that the vast majority do not do.
You'll want to prep well ahead of time for scenarios and categorize players - I do it by using 3 categories that I denote - X, Y, and Z.
X are the consensus best options that I'll slot into lineups that have the best odds of winning.
Y are the boom-bust players that I'll put into lineups that are a bit behind but need leverage to win.
Z are those I'm expecting a min. cash with so I'll put in a guy with a high floor with no ceiling (not looking to win).
Examples of these type of guys in week 1:
X - Keenan Allen/Josh Jacobs
Y - Cole Kmet, Darnell mooney, Dallas Goedert, Tyler Higbee
Z - usually a Hunter Renfrow type, kickers/defense
Autopsy of my 3rd place finish:
In week 1, I liked the late slate of games more than the early slate so I knew that I wanted to go with 3-2 and 2-3 lineups leaning more towards 2-3. I constructed my primary stacks:

And I constructed my shells:

Preparation is king and I had the links to every contest, a spreadsheet of what lineups players were in with live scoring, and a list of my preferences for X, Y, and Z options for both SS and non-SS.
As the early games were ending, it was clear that I had 4 lineups that were in contention and I had a real sweat going:
It appeared to be a low scoring day and was looking like top 10 would be ~120 and a takedown ~135.
Superstars are the MAJOR point of differentiation and to overtake someone you will typically need the combo of your own SS + top SS’s skill position to beat the top SS + your SS’s skill position.
As a side note: last year SS RBs and WRs were in the winning lineup at ~ the same frequency and SS QBs were about half of that. Typically, it is much easier for a RB/WR to score much higher than others in their skill position than QBs and I lean towards WRs as their ceilings are typically higher.
The two combos SS + 1 combos to beat were:
Cousins + Jefferson @ 49.46 pts and
Richardson + McCaffrey @ 50.82 pts.
Aiyuk was the top scorer by a large margin but was relatively low-owned so I did not have to worry about many others having him.
Thought process:
For my first lineup, I had the top stack as well as the top-scoring RB that was decently owned. I looked at the lineups around me and for all intents and purposes,
this was the lineup to beat. As this was the case I wanted to play the best floor-ceiling combos for which I believed to be the following:

With the next two lineups I had to make a decision. I knew that I had to beat 49.46 to 50.82 points and felt that the stacks in the Dolphins/Chargers game had the best shot of doing so. I now had just to decide which side I liked better. I was pretty lucky to have 3 shells to swap into so I decided I wanted to not overlap players too much.
It was very close but ultimately, I thought that Herbert/Williams had a better shot than Tua/Tyreek as they were the home favorites. I slotted as follows:
With the last lineup, I had a 3v3 where I needed McCaffrey + a non-superstar stack to beat out Kirk/Etienne/Jefferson for a difference of 42.56. I considered Tua + Waddle but did not want more exposure to that game so I ultimately went with Love + Doubs, opting for the bring-back in Kmet which in hindsight was a mistake. Kmet just didn’t have the ceiling necessary (tight ends rarely do) and I should have gone with a number of other X/Y options with higher ceilings.
With my decisions made I frantically swapped to meet the deadline and as 4:25PM arrived I got up from my desk to finally eat the first meal of my day

. As the 4PM games were coming to a close something became abundantly clear:
You needed Tyreek Hill to win.
The Tua/Hill stack demolished the Cousins/Jefferson one (by 30.18 points) and nobody else came close.
These 4 lineups placed 3rd, 57th, 73rd, and 150th for a nice payday of $8300.
How did my other lines do?

Allen and Waddle met their high floors but did not reach their ceilings. It’s possible I could have arrived at Aaron Jones instead of Waddle for 14.9 more points (28th place finish) but I don’t think I would play this differently.
Similar story here except that Mike Williams got injured. I could have played the Tua/Hill stack here and taken 2nd place but I again wouldn’t change anything as I thought that Herbert/Williams had the better potential.
This one did really well outside of the mistake in Kmet where I should have played any of the X options outside of the Dolphins/Chargers game. These 6 potential players ranged from -5.9 to +8.3 which ultimately did not matter too much, but EV-wise it definitely mattered a lot.
It’s an incredible feeling to see the preparation and grind pay off, especially in week 1. It’s even more rewarding to have all my friends in MVHQ cheering me on as well. Hope this helps you think up some strategies. Stay tuned for an upcoming section on deep roster stategy!