I might be moving into a new house soon (unconfirmed as of yet, but will want to get advice so I can immediately start as soon as I move).

It is already built, with ONT in that distribution box inside the garage, which connects to house's internal wiring that has ethernet jacks in various room walls, so changes probably can't happen.

In my current setup, I have ditched the ISP modem/router and connected my own router (RT-AC68W) directly to the ONT that's in my room. A few PC's and a server are connected to this router via ethernet.

In the new house, will I be able to either:

1) Ditch the ISP modem (If that's provided? Never seen the inside of that box so I have no idea how it works or what's inside), connect ONT directly to internal wiring, and then connect router to an ethernet jack in a room upstairs to serve my machines from that router?

2) Ditch ISP modem, connect router directly to ONT and connect that to internal wiring, then upstairs I add a switch to an ethernet jack?

Wireless is not an option for these, especially the server.

Second question would be if I were to rent out a room or 2 where those rooms have ethernet jacks, how can I provide possible tenants with an isolated connection via ethernet, or possibly disable the ethernet jacks and provide an isolated wifi connection?