It'd be nice to have a UI where you can set things like max connections, wal_level, etc. when you need to go beyond the defaults.

This can be done in a hack-y way currently by modifying the start command of a Postgres instance, e.g.:

wrapper.sh postgres --port=5432 -c 'max_connections=6715' -c 'shared_buffers=1GB' -c 'work_mem=32MB'

But that's not very user-friendly.