We would recommend that you start out with the Deluxe 1000 web hosting plan, as available on https://www.ultimatewb.com/domain-names-web-hosting . But you can start with the Starter plan when you develop/create your website, and then upgrade when necessary.
Yes, you can switch web hosts if you would like, to another server/web hosting company. You can provide them the Server Requirements page at https://www.ultimatewb.com/server-requirements to check with them that they meet the server requirements.
You need a domain name, web hosting, and the software license. We connect your domain name to your web hosting, and then your domain name is hosted. Then we install your software on your web hosting if you are hosting with us (installation is free when you use UltimateWB web hosting, but does require separate software purchase).