Planning to 100% all Far Cry games. Any tips?

I haven't played any Ubisoft games before and was holding them until they get achievements and now most of them have achievements now (This isn't the only reason anyway but np).

A friend gifted me Far Cry 5 so I'm playing it now so I will start with Far Cry series and move on to Assassin's Creed after this. I know how grindy are Assassin's Creed games from people but Far Cry 5 don't seem to be grindy or hard.

Anyway what should I expect from the series? There is 7 titles with achievements excluding Far Cry 1&2.