I've tried granting on both Luckperms and FTBranks the permission " meta.xaero.pac_max_claims.9999" and "xaero.pac_max_claims: 9999" for the respective mods, but neither of them seem to override the server config limit of 16 chunks.

OPAC ver: 0.20.0
FTBranks ver: 2001.1.3
Luckperms ver: 5.4.102

Using all of these in the Prominence 2 [RPG] modpack as well.

You're supposed to set an integer permission "xaero.pac_max_claims" on FTB Ranks and an integer meta value on LuckPerms. Not a regular true/false permission with a number at the end.

Can you provide an example of what this would look like? Because "meta.xaero.pac_max_claims.50" permission on luckperms does not override the default config either. I'm not sure what permission on FTBranks I'd set that'd work.