This is a pretty good resource for some basic tuning (mostly buffer sizes and connection count): https://pgtune.leopard.in.ua/

Yeah mostly just keepalives and timeouts, increasing kernel maximums for connections, using Unix sockets directly instead of tcp, using pgbouncer, etc. as always, depends on use case and monitoring and measuring to determine your needs is good.

man, i wouldn't worry about tuning something like TCP until you can reliably prove TCP is the bottle neck in performance. That day will likely never come for most companies.