The firmware issue is probably very individual device dependent. I remember the old USG plus an old cloud key (both no longer sold for a long time) had some st

The firmware issue is probably very individual device dependent. I remember the old USG plus an old cloud key (both no longer sold for a long time) had some stability issues maybe two or three years ago if you enabled every possible monitoring feature simultaneously, that issue is long gone. UniFi is much like MS or IBM in that they sell such an incredibly wide range of products its quite possible our experiences have nothing in common. The original cloud key is quite slow but totally usable; there's a docker container and running on anything faster than a Pi its quite fast and snappy.