Depends on your requirements, obviously. I have a 1300 SqFt 2bhk and a well placed AP
AC Lite is giving me more than enough coverage, and is stable enough so that interference from around 10 networks that my devices pick up (damn them neighbours!!) isnt an issue.
Firstly you'll have to decide where to put your access points. Then, you'll need to stick to your old modem/
router (My clunky dabba given by
tata broadband works as a router/modem, ive disabled the wifi radio)
Any AP AC would do well, an LR gives you longer distance but its radios give it a more "donut shaped" coverage pattern, away from the AP itself.
The PRO has more antennas. and the LR is the entry level of the three, but still above and beyond your consumer/prosumer routers.
You need to remember though, there is no "AP" interface, all the configuration to the AP is done via a controller that has to be installed either on a PC or a Mobile Device. So people even "somewhat" experienced with networking might get lost if suddenly your AP drops out and you need to SSH a firmware on it (not that it happens often, or at all.. in my experience)