Do you want to completely replace the file system storage with a database?
In that case, you’d better go with a CMS that uses a database by default.
The idea of connecting to a database is to do that for specific content, because you need a model for each content type. Where you need to do that is all explained in those guides you mentioned above.
It is not the intention to replace the system completely. I think so for now.
The key question is if a low-budget server can handle multiple users working simultaneously on the panel.
I am only experienced in using Kirby as a single user. Are there any known issues?