Hi guys, I've had a read of the comprehensive router guide sticky and a few other threads like this one about hardline home networking, but I think I'm missing something fundamental about combining a switch and a router vs just a router.

My apartment has 5 ethernet ports distributed throughout it. The ONT lives in a cabinet hidden away in a wardrobe at one end of the house. Planning to put a router in the cabinet and repurpose my aging DSL-AC68U as a WAP-only. We're on a 900/400 connection and do a lot of gaming and streaming, so want to get the most out of the hardwire connections.

I was looking at the EdgeRouter X / 4 / Lite and the Mikrotik RB750Gr3 suggested in the review thread, but they only have 3 or 4 LAN ports. So to cover the 5 connection points through the house, am I better to:
a) Use one of these routers in combination with a switch, or
b) Buy a larger, more expensive router like the EdgeRouter 6P or Mikrotik RB3011UiAS-RM ?

Might be asking dumb questions here, but I don't understand the pros and cons.