could I expect a faster system if I would migrate from mariadb/mysql to postgres?
Google is your friend:
I did not do a proper comparison - everything the same but the underlying database.
But I have used different combinations of web server/database for many years.
The postgres database is used in Hansson’s VMs that I use in Talk servers…
From my experience there is no noticeable difference on the user end with under 100 users and under 500GB data…