@MagicLike I'd sooner use prefab SMF cables (or even MMF) and not worry about the pain of (what amounts to) 10Gbit modems.
You're trying to live on the bleeding edge where little else is - why bother?
Finally you're conflating Layer 3 and Layer 1 stuff; switch is a switch, router doesn't enter the picture for LAN-to-LAN stuff, except maybe to do your DHCP.