If we split ranges (we're not using a pure bet/pure check strategies) we need to have nutted combos on runouts that complete draws (flushes/straights). This is also defined as not capping your range, as if you never check 8 outs straight draws or flush draws you're going to be capped on turns/rivers completing the draws.

If you check a lot on a board texture (f. ex. 2 4 5 BTN vs BB SRP) you also need to check 2p/sets type hands -this concept is more relevant in HU play, as there are more offsuited nutted combos, but also applies in 6max-, as your opponent will put a ton of pressure on your wide checking range if you check and you want to be able to represent the nuts sometimes. If you almost pure bet, checking 2p+ hands is not that important.

The core concept is that if you're capped your opponent can start to use huge bets with thin value hands -f.ex. TPTK if you're capped at TPTK and never have 2p+-. You say you only face 1 overbet or 2 at most, but the problem is that we play no limit, so the overbets can be for the stack if you're extremely capped. And the more capped you are, the thinner they can go for value -and if you never bluffcatch, they can just blast off their entire bluffing range-.

That's why simplifying when possible it's a good strategy, as you don't have to worry about having a capped range, but this can be problematic against extremely aggressive players that are going to check-raise and float very aggressively and blast off with overbets if you check.

On the turn we almost want to pure bet nutted hands, the exception is on very dynamic boards where the nuts can change often on the river -f. ex we want to check some flushes, straights, sets, and two pairs in boards including flushes/straights- and the reasoning behind the checking FDs and straight draws still applies on all sort of textures.

Yes, I was referring to the part of your question where you asked about IP Turn cbetting. I develop these concepts in my video "Global cbetting frequencies and bet sizings in 3bet pots". OOP play is discussed there, although in 3bet pots, but the main concept -the harder your range hits the board, the more you bet- still applies in SRPs.

To summarize an answer to your question we can say that slowplaying frequencies usually increase when the global cbetting frequencies decrease. Also there might be some exploitative reason to have 0% slowplays against certain player profiles (mostly passive-stationy opponents) and to increase slowplay frequencies with non-vulnerable hands against opponents that massively overfold.