A banana pi is not going to have the processing power to properly route that much data.
You’re looking at an Intel nuc at minimum.
If your internet is 5gbps and the router only has 2.5 gbps ports, you’re going to be capped at 2.5gbps unless you start getting really over complicated because the router expects ONE incoming port. There ARE ways to support pairing two Ethernet ports together, but your ISP’s modem/router won’t support it because “fuck you for having your own hardware”
Also because they’re cheap.
If your switch is 1gbps, you’ll be limited to 1gbps.
Going from “sim “ to “voip” means that your cell phone will only ever work when it’s on wifi. The reliability will drop significantly Your ability to get maps and things while on the road, in fact you won’t be able to receive or make phone calls/texts/anything while travelling at all (by bus, car or bike)
… just fyi