The idea is you really shouldn't care about the environment in any way. Thats our job. Ask yourself, do you want to look at server parameters, or do you want to run a community? Most people, in our experience, play with servers for one of 2 reasons. They either enjoy it (no idea why lol), or they have simply always done it that way. Most fall into category 2. As mentioned by Randy above, most tend to find the idea of letting go harder than it actually is.
In terms of which plan to go for, you wouldnt be lookin at cpu/ram etc. Again, boring. Thats our job. The only consideration is storage, and what features you want to be able to use. You can see all of those here
https://invisioncommunity.com/buy
You can indeed. I see you are currently using a subdomain. What would happen, is once you are moved over and you have checked to ensure things are as expected, we would provide you with 2 CNAME entries. You add those to your domain, let us know, and we take care of the rest
Support is the same in terms of the software, except you can contact via email if needed. Of course the main change however, is we are in charge of your hardware environment too. So essentially, if you have a problem you contact ourselves unless it's a 3rd party item or something you control yourself such as an external email service if you decide not to use ours.