Have a look on the serps and see if a one operator site ranks anywhere in the top 20 and base your decision on that. The more topics you cover the more KWs you can rank for, you really limit yourself with just one operator.
I have used nitropack and yes it does give amazing scores but there is a lot of reviews online about it as you say saying it tricks the score.
Speed optimisation is not something I'm clued up on but did read quite a lot of info on nitropack
I have a few on siteground and no it's not amazing, hence me looking to jump ship. The SG cache plugin doesn't seem too clever either and I'll be switching to WP Rocket next week