I checked both your accounts and none has connected to our hosting so I can't really check that. And yes, since our hosting has built-in optimization like caching, then there is no point activating another plugin that does the same. We strongly discourage activating multiple optimization plugins even on another hosting platform, since it's overkill and mostly have bad effects instead of doing good. What I'm referring are the caching plugins and not other plugins listed on this thread.
And to answer the thread's question, yes, you can use cache plugin and SEO plugins on Pro theme, but it depends on the hosting.
And if you have issues activating other plugins then please contact us through our hosting panel and create tickets