So, HTTPS prevents people on the network from hijacking the connection or spying on what you do with the website or your passwords. If you have a VPN and no evil devices inside your network you are likely fine, and many things don’t need HTTPS-level of safety.

That said, browsers make using HTTP almost unusable nowadays, because over the internet you really want your connection to not be hyjacked, and almost nobody self-hosts (sadly).

I would reccommend to set up a reverse proxy to do https for all services you host, even if you only use it via lan/vpn. Adding a new service then becomes just hosting it over HTTP, and have your reverse proxy converting the connection to HTTPS.

If you have a domain, you can request a wildcard cert from let’s encrypt and use that also for internal domains (they don’t need to be reachable from the public internet, but you might need to expose the ACME challenge file).

If you want to learn a lot about certificates you can go the self-signed route, but you’ll have to install the certificate on every device you use to access your services (guests will get huge warnings when trying to access your pages, if you give them access to them). Once set up it’s more flexible though, and if you configure your dns server you can have whatever domain you want, even nonexistent or unavailable ones.

Wine/proton are not emulators, they run the code directly on linux, but using some fancy tricks to rrimplement windows dlls into linux native code. If someone embeds linux code in the windows executable you have the same privileges of your user and at tgat point you can be infected with a linux virus.

It’s not likely today because windows is much more popular, but once linux becomes popular enough to be an attractive target you will need to be as careful as on windows.