Which Wi Fi Router do you recommend? And also another question
 

D-Link AC1750

Netgear Nighthawk AC1750

And why do I see quite a few routers with the same model code "AC1750"?

very happy with this one

TP-Link AC1750 Smart WiFi Router - Dual Band Gigabit Wireless Router, 802.11ac Internet Router,

I have a Netgear that I'm very happy with, but it's in a location that makes checking the model number quite difficult.

I had a Belkin that I really didn't like because I did not like the user interface.

AC1750 is just to help consumers decide what soft of speed (range) they may expect from the router.

Reading online review websites and customer reviews may shed some light on your choice. The prices are similar.

I'm most pleased with my TP-Linc AC1900 - but I think there's a newer, better model out now.