Hi Jan,
the current Qt Marketplace versions support Qt Creator 6, so I would recommend to use those if you do not want to use Qt Creator 4.x.
Support for Qt Creator 7 for Felgo 3.x will likely come with the next update. We are currently also preparing a Qt 6 based version of Felgo which will then also support the latest Qt Creator version.
Regarding Felgo Live, you could also make use of it without the Felgo Qt Creator plugin. All you need to do is to start the Felgo Live Server exe (located in /Felgo/FelgoLive) from the command line, with your project path as parameter, for example:
C:\Qt\Felgo\FelgoLive>FelgoLiveServer.exe "C:\Git\somedemoapp"
Best,
Alex