OK - so so many great suggestions. I am distilling the options one at a time.
EU4/CK2 and indeed HoI2.... Im going to hold off. Not least because I cant make my mind up which Id prefer. There is a considerable outlay as DLCs can add up and some seem pretty necessary to unlock key features. There all relatively old games - and from what I gather EU5 is in development. They all have demo versions, so I can have a tinker, and with so many other great games to look at - Ill put this genre on the back burner for now.
AC - Origins/Odyseey - same here. Having not enjoyed Black Flag (or AC2), and while understanding these are not the same - more RPGs - there are titles from Devs I KNOW I enjoy - Cyberpunk and Outer Worlds - due out relatively soon. Ill play other games first and pick those up at (or after) release I think.
I am Definitely picking up Divinity Original Sin 2 for an RPG, and Anno 1800 for resource management - probably in that order with a space combat think in between.
Im also definitely picking up EITHER X4 foundations or Elite Dangerous. Not sure which though. Loved the original Elite (on a BBC-B computer in the early 80s) and Dangerous on PS4 a couple of summers back. However, having played ED before..... I know the PC version will be FAR superior graphically, and in the last 2 years will have developed from the console version I played - Also having a "new start" with re-ignite my love. However, I didnt enjoy mining, or exploration that much (exploration was better but after a while just got samey). I did like trading and combat. the grind is big here though. I havent even seen an X Game - and while graphically it seems inferior to ED - gameplay wise it might suit me better.
So - unless anyone has anything else left field, or cares to help me decide between X4 and ED, Im pretty set.
Thanks for all the suggestions, incites and advice.