I made a Github gist that lists some tools needed and has instructions that should deal with these files:
.xp3, .amv, .psb, .scn, .psz, .int, .hg3, .cst
This is mainly written for all Nekopara games (Vol. 1, 0, 2, 3, and Extra), but it can also be useful for other VNs as well
Here's the link: https://gist.github.com/LukeZGD/64b0ecfb7eaccdfbb327ddfea4621723
Also this covers extracting/unpacking only. This does not cover repacking