@Nadahar It’s much less complicated than you apparently think it is.
The semantic model is essentially just additional groups and tags, and strictly speaking doesn’t even impact MainUI. If you use it, it tags your items and adds them to groups.
The default MainUI entry page called “overview” then uses this information to present users a default view on their home.
From there on, however, you can change or even replace the overview page, and of course you can add your own pages and use those instead of the autogenerated view.
There you’ll be having all the display flexibility you might want. You can even keep your items tagged, that shouldn’t do harm as no OH component except the semantic modeller should be relying on them.
(Well, parts like voice assistants eventually can make use of them, but they do not rely on it.)
That’s it, essentially.
(@rlkoshak I tried boiling it to the point and might have overlooked things in doing so, so please correct me where needed)