WordPress will run on a toaster these days, it really doesn’t have high requirements. Just make sure it’s a Linux server, any comapny worth anything will have PHP and mySQL up to date enough for WordPress.
What your’re going to have to struggle with is different companies offering different packages and then not being fully honest. A mid range package on one service may be worse than the cheapest offered by another because they sneakily overload their servers.
Remember than even on the “cloud” your site still runs on a piece of hardware that is going to be getting shared with others unless you jump onto a dedicated server off the bat.
My advice is always do your research on the company and reviews, don’t go in for a long term contract and be prepared to jump ship if you don’t get the service you need.
Remember that WordPress has a lot of plugins for caching and speeding up sites, these usually also come ready to tie into Content Delivery Networks that can help take the burden of delivering your site to your viewers as well which means a slow server don’t impact your users anywhere near as much as without a CDN.