Long Time CK2 Player, New to CK3

After the Chapter 4 announcement, I finally decided to pull the trigger on getting CK3 after holding off and not being to interested until now. So with that said, what are some new or different things to explore in CK3 for a CK2 veteran? What are some "must check out mods"? What are suggestions on reforming and hybridizing cultures? With how faiths are different than the faith/heresy system in CK2, how do you switch faiths in CK3?

So far I started a campaign on "noob island"(Ireland) and found the transition pretty easy so far. Just would love to hear suggestions and see what other recommendations people have!