I really like how this mod makes it that you can't capture bosses, but for some reason people can capture wardens and/or mini bosses from other mods.

Perhaps you don't consider the warden a boss but I do especially since i dont want anyone finding other ways of cheesing him.

[Actual Request:] So I think a good solution is to make the mod configurable where to we can blacklist mobs that we don't want being able to be captures

Portable Mobs already has a portablemobs:capture_blacklist tag for blacklisting entities.
https://github.com/Dremoline/PortableMobs/blob/1.21.1-fabric/src/generated/resources/data/portablemobs/tags/entity_type/capture_blacklist.json