I have on my website jetpack cdn +jetpack boost enables
cloudflare cache plugin
In cloudflare I have two rules: cache everything
and wp-admin cache bypass
But cache everything my site loads in mobile and on desktop with an blink of an eye 0,5 seconds, ttfb speed is fantastic see both screenshots desktop,second screenshot on mobile phone.
Cloudfares rule cache everything is not for everyone, some wp themes will break, had this experience with some of my clients who hosted on ionos I can not say if it's caused by ionos or by the wp theme.
You can tray it to see if that works for your site, when it works you will impressed by the immense speed boost!
on android ttfb from 50ms to 110ms
on desktop ttfb from 150- 250ms (both screenshots from keycdn performance tool)
and I be on low entry fastcomet wordpress hosting plan.
I hope that cloudflare is not bad for my seo rankings and this cache everything rule will not bad for my seo too.
When you decideto go to DO or Vultr your speed will not be faster , or otherwise you will get same speed without need cludflare/ or other cdn.
When you site is getting errors on cloudflare, remove it then add it again, check if you have set the cloudflare nameservers on your domain registrar. Maybe use another cdn provider who has a wordpress plugin where you insert the cdn cname url ( I find this better as changing nameservers).