Home Networking

That’s not how any of this works. Any somewhat modern router/modem combo will not be a bottleneck as far as speed is concerned. Switching and NAT happens in-hardware at speeds that are negligible to your internet speed. There’s no such thing as sending the “excess” internet to another device.

If your router performance is struggling you can get an aftermarket router but you’ll always be limited by whatever speeds your ISP provides.

Do not attempt to plug your computer straight into the modem. It’s obvious you aren’t familiar with exactly how a router works and you’ll be leaving all your computer’s ports exposed to the internet without your router acting as a firewall.

You can do it, but it is not recommended! I would do it shortly, just to test speeds or something like that, but wouldn't keep it permanently like that!

The router "protects" you from the outside world, as you are not exposed from a security standpoint

It's overkill for what it sounds like you need, but something like the TP-Link ER707-M2 would give you the speeds your asking for, for a not unreasonable price.

https://www.amazon.com/TP-Link-ER707-M2-Multi-Gigabit-Integrated-Protection/dp/B0C238XMVV/

2.5Gbps WAN, 2.5Gbps LAN, plus additional gigabit LAN. You'd need to add a wireless access point for your wifi devices, but those can be had cheap. Hook your modem up to the 2.5Gbps WAN port, and your computer to the 2.5Gbps LAN port, and you'll get max speeds. And you should be able to limit the wifi bandwidth either on the router or the AP, minimizing impact on your wired speeds.

Personally, if I needed 2.5Gbps, I'd invest in a Firewalla Gold Plus, but I just really like my Firewalla Gold.

All that said, I don't think you mentioned what your provider speed is. Unless you're getting more than 1Gbps from your internet provider, you don't need this. Also, of course, your computer would need a 2.5Gbps network adapter, but I assume you have one already (or a plan to get one).

Ask your ISP to put your modem into bridge mode.