You added an Ethernet line from basement to floor above so there is no reason for a fiber media converter. I would get a 4 node tri-band mesh system, two will be wired and two will be wireless.

Make sure your NIC is set to full duplex and auto negotiate or 1 gig.

I’ve always perceived power line adapters to be trash(based on using them 10+ years ago) but I had to use one out of necessity recently and it actually wasn’t bad.

100mbps is fine for three people. What is your current speed through spectrum?

You and your roommates should split a 4 node mesh system. Main one goes where current router is, and you each get one in your room.

Any wifi 6 system will work just fine.

Some of the smaller ISPs may offer fiber. Would be worth it to check them out.

If running lines in your house isn’t an option I suggest connecting the meshes to your consoles/pc directly with an Ethernet cable. Only way to get 1gbps reliably is with a wired connection from main router to device. Upgrading to a wifi 6 mesh system will probably help some.

I would just get a router/mesh system that has good parental controls. You can set time limits or manually turn internet access off to certain devices.

A quick Google search suggests TP-Link Deco WiFi 6 Mesh System for good parental controls.