What happens if I turn off Spectra Plugin?

Hi,
I am not sure if this is a stupid question but can anyone let me know what happens if I turn off the Spectra Plugin?
I was basically auto-forced to use this Plugin when I updated my previous plugins (I think this is the successor of Gutenberg, isn’t it?) and it is simply horrible to work with. The plugin slows down the editor in an extreme way (the rest of the page and backend works well), it doesn’t matter which browser or device I use. Editing and working with it is close to impossible.

So basically my questions are:
– if I turn off the plugin, will it break the site? (because it basically took over the editor and many settings)
– if I turn off the plugin, will I still be able to use the old UAG – reusable blocks? Will they still be shown or will the old blocks break/not be shown anymore?
– is there a way to get back the old Gutenberg Plugin with UAG?

Thanks for your experiences, maybe someone has done the same.
Chris