Should I revoke login from the default pgsql user?
You will need a superuser that can login for administrative purposes. So don't change the existing superuser to NOLOGIN unless you create another superuser first (but tgen you could just as well rename the existing superuser). The secure thing to do is

use a good password for the user

severely restrict access for that user in pg_hba.conf, ideally to local connections


There is one scenario where you could change the only existing superuser to NOLOGIN: create a regular user admin with NOINHERIT and
GRANT chris TO admin;

Then admin can always assume superuser privileges with
SET ROLE chris;

This setup has the advantage that you don't need a shared password for the superuser. Each administrator can have her own normal user that can assume superuser privileges when necessary.