I saw your recent Weilong avg12 video, you wouldn't mind if I gave you some tips, right?
1) Cross
Try executing it faster, you can plan it well in inspection from what I saw, just try doing it faster, don't try to look where the cross edges while you solve it, that'll lead to pauses, just try memorising the moves in inspection, it's okay to use a bit more of inspection time. For an ideal sub-20 solver, cross should be around 3 seconds, yours are around 5, in some 3-4 solves I saw pauses before solving the 4th cross edge, try working on that, if you actually plan your cross wholly in inspection and solve without looking at it you might actually be able to lookahead into the first F2L pair easily.
That was one long sentence OMG
2) F2L
Pauses are still there, try looking ahead a bit more, unnecessary rotations like y2s and y3s should be eliminated, I guess doing slow solves, where you try to solve F2L with the least number of rotations will do the trick for you, also try inserting F2L pairs from different angles with R' U R, L U' L', etc, when I was averaging 26 I got an 18 second official solve ONLY because F2L had just 1 rotation, that shows how important minimising rotations are. Slow solves will help you in all of the above aspects.
I must applaud you for your pair insertion-execution though, excellent, better than mine, teach me pls
3) OLL
Try increasing tps a bit more here, from what I saw your LL tps was almost the same as F2L tps. Also get better algs, for example F (triple sexy) F' can be done in a better (IMO) way as R U2 R' U' sexy R U' R'. Drill all OLLs to increase tps
4) PLL
Same as above, though I don't think you need better algs, just drill them and try executing them faster, maybe look on Youtube for better ways of executing/better fingertricks, jskyler's channel is one of the places where you can learn this
EDIT: also, what I think ideal splits for a sub-20 solver are is 3-10-3-3, compare yours with that and work on the part which needs most improvement