What exactly do I need to know to figure out if I can use a router/modem combo instead of the "all in one" provided by my ISP?

Hello there r/techsupport!

I live in El Salvador, and I have a 25Mbps/5Mbps connection. I used to be able to play on my Xbox one perfectly (over Wifi), but lately I've been having problems with lag.

I have a Technicolor modem/router combo which seems to need a reset every 24 hours. How can I find out what hardware would work with my ISP (Claro El Salvador)?

Thanks in advance!