Can someone name a body replacer with pussy/anal - physics/collisions that works for you personally as it should when you playing animations?
Some collisions are added by animators - my guess is those rule34 videos use those animations. As long as the body mesh is weighted for labia and anus nodes, animations that work on those bones should look fine.
As for general collisions, it depends on a lot of factors, not least of these are actor scale and alignment. My very superficial experience hints at that BHUNP vagina works well with SMP collisions, as long as the male body is also using SMP (you can pick during BHUNP installation between SMP or CBPC collisions for each general body area). 3BA works best with CBPC collisions (they're not as tight, opening clearly happens ahead of penetration because of how the spheres are set up, but you can pick camera angles where this isn't so apparent).
For CBPC. collision spheres are set up in those CBPC inis. Both 3BA and BHUNP have their own setup integrated and that does NOT look tight in sex animations. You can tweak it. The caveat is that the smaller the spheres, the less tolerant to misalignment. I prefer to have average sized spheres that normally cause labia to react even when there's a misalignment with the male parts - it's a bit like having xVASynth audio rather than silent lines. Not great quality, but some responsiveness is better than feeling like meshes don't have those animations enabled at all. I don't do videos, though.
SMP is trickier, its collisions are much more realistic when they work, but it's very sensitive to correct alignment. If you're playing with a lot of different SLAL packs, it's a drag to get them to all to align perfectly. Personally, I don't care about shortstack or giant characters and set Sexlab to reset actor scales during scenes - that, at least, lets me exclude any and all non-equal scaled animations (usually referred to as big/small/1.2 scale, etc) and align the rest if they aren't well aligned to begin with. If you play with different scaled actors, this is a lot more difficult to maintain. COCO body had its own SMP xmls and worked very well for me with no tweaking of mine.
Also relevant is whether Sexlab is set up to compensate of heel height or not. I feel like heel compensation doesn't work very well, so I disable it and just force sexlab to strip shoes off characters - you lose scenarios where you might prefer to see those heels on, but at least alignment follows the general rule and works best in most situations.
If you use mods like Better Female hands wrists ankles and leg ratio twists for XPMSE, or Vera's skeletons, or even NPC mods with custom skeletons, there's a big chance they break alignment in Sexlab animations, too.