7.4 should still has some issues (warning in the core and bugs in themes). I've tested up to 7.3 and it worked for 1.2.x.
I'm running on litespeed, mariadb, ssd, and php 7.2 with apc and litespeed cache module. 3 stores, 1 WP site.
It all depends on what amount of customers do you expect and you can upgrade from here but this is working just fine for me.