If ordering the Basic package from https://www.discourse.org/pricing:
-where is it cloud hosted (server location)?
-where/what takes care of the email when cloud hosted (since I read one needs a separate email provider), while it mentions ’ 50k monthly emails’
-how is the domainname done, since it has no ‘Custom domain’ option?
Self hosted question:
-if self hosted, are there no restrictions to plugins and features, ie does one get the full feature set, with unlimited admin/mods etc etc?
Hello and welcome @SjefRomijn 
You can choose your server location on signup, from either the US, Canada, or the EU:
If you’re hosted with us we also handle all of your email too, so no need for a separate provider. 
And for the Basic tier your domain would be SOMETHING.discourse.group (though if you ever upgraded to Standard you could then use your own domain if you wished).
We would also handle all of the technical side of things, as well as providing a dedicated support channel for any issues or questions you may have.
If you do choose the self-hosting route then you can install as many plugins as you like, including third-party ones, and have as many admins and moderators as you like too (though a good alternative regardless of hosting is to use TL4 and category moderators instead, as they have some mod-like abilities without needing to be full forum staff members). And if you opt for the standard install method you can access help from our very knowledgable Discourse community here on meta too.
