IIRC TCP/IP through localhost actually benchmarked faster than Unix sockets because it was optimized harder. Might've been fixed now. Unix sockets gives you the advantage of authentication based on the user ID of who's connecting.

My experience with sqlite for server-based apps has been that as your app grows, you almost always eventually need something bigger than sqlite and need to migrate anyway. For a server-based app, where minimizing deployment complexity isn't an extremely important concern, and with mixed reads and writes, it's rarely a bad idea to use Postgres or MariaDB from the start. Yes there are niche scenarios where sqlite on the server might be better, but they're niche.