250 Mbps from ISP. 686 Mbps Cable modem. Is the modem powerful enough?

"Hi Jacob, Please share ISP you are using.

One way to confirm, you can actually call your cable provider to confirm.

I guess is to just provide them the MAC address and they will do the provisioning at their backend.

https://www.bhphotovideo.com/explora/com..."

Yes. If the cable modem can provide greater than or equal to the speed of the internet connection, it will be fine.