As no-one has replied I will try to help. I do run my own Joplin server but I do not use profiles.
Firstly there are two versions of the Joplin "server" available. There is Joplin Cloud which is the version you pay for per user account and is hosted by Joplin. Then there is Joplin Server which is the free, personal use only version you self-host using docker. With the self hosted version you can set your own limits for accounts so you can give a user a much more generous amount of storage or note size than even a Pro account on Joplin Cloud. You can create as many accounts as you like on the server.
When you set up profiles in the Joplin client they act as two totally independent versions of Joplin with different sync targets, plugins, everything. When switching between them Joplin shuts down and re-opens as if it were a totally different install. I am not sure that it would be possible to copy / paste notes between profiles unless you just copied the body of a note and kept it on the clipboard as you switched. This method means that you do not get any linked resources transferred as well. A possibly easier way to move notes between profiles for testing would be to export a few notes from your main profile into a JEX file or two and then import them into the second profile after switching.
There have been relatively recent changes to the server and now a pro user can share a notebook with another user who is on the same server, pro or basic. The pro and basic users can work on the same shared notebook. A basic user however cannot share a notebook to start this process for themselves. Both pro and basic users can "publish" a note which turns a note into a static web page. Anyone can access and just read that note if they are given the URL, Joplin user or not.
If you want to just explore what you can do with Joplin when connected to a Joplin sync target it may be better to create your own local Joplin Server using docker and have a play with nearly all the available features, creating as many accounts as you need. Then, when you have got a feel for what you can do you can purchase whatever level of Joplin Cloud account you need and as many of them as you need.
The teams account plan refers to having "share permissions". I do not get that on Joplin Server so I have not seen how that works.
As for the Joplin Cloud servers...
I hope something in that swathe of text above helps 