For 4x4 BLD corners I use Old POchmann so what's the parity fix for that?

Old Pochmann can be a problem with big cubes because Y-perm rotates the U-centers ccw 90 degrees. So if you're executing corners before the centers, you have to keep track of how many Y-perms you do.

An odd number of Y-perms will obviously swap the UB and UL wings. Therefore they can be restored by doing B U' B' (r2 U2 r2 Uw2 r2 u2) B U B'.

However, r2 U2 r2 Uw2 r2 u2 is not center friendly, so this parity fix will have to be done after the centers are solved.

Alternatively, you could solve all corners except leave UBL and UBR swapped. Then have the parity fix as y (T-perm) y' r2 U2 r2 Uw2 r2 u2.

There are many different ways to approach this, you shouldn't have to rely on the forum for answers, do your own experimenting.