Hello,
We use Hetzner hosting for our demos. Many of our users use Bluehost, LightSpeed< Siteground. So, choose the one that suits your needs most of all. Theme requirements you can find here - https://www.8theme.com/documentation/xstore/theme-installation/xstore-theme-requirements/
The Ajax “add to cart” timeframe depends on server response time and DB optimization structure.
Regards