Logseq with Syncthing if you want cross device operation.

My vote goes to Zola, too.
I recently migrated my Hugo blog to Zola.

Yes, you need to buy (register) a domain beforehand.
The e-mail provider of your choice that provides custom domains will ask you to

• either point your domain to their nameservers (done from the domain provider’s panel)
• or insert/update some DNS records on your domain (either from your domain provider’s panel if it is supported or you can link your domain to another DNS service e.g. CloudFlare)

Cheers! 😉

This might help you: https://iliasa.eu/wireguard-how-to-access-a-peers-local-network/