See the link in post 3. You will want to go for a Pi 3 and openHABian. Anything beyond is possible but only recommended to OH experts that know how to properly install Linux derivatives and OH on top.
No, wear levelling does not always apply and the larger your card the longer a raw backup will take, and backups are the most important part of the story. Read on.
I’d suggest 8 or 16 GB at most, even 4 will do (if you still find someone to sell them).