802.11ac will have less coverage than 802.11n routers running on 2.4g because 5g is more easily blocked by walls and such. The testing I have seen on beamforming in a house is inconclusive if it makes much difference. The theory I have see discussed is signals that bounce off wall and say go around obstetrical may work better that tryng to force a signal though a wall. If a mirror or some other dense object just happen to be at the point the signal tries to go though.
Almost all routers put out the legal maximum power allowed by law. There are only tiny difference between models. Your end devices make much more difference since they all do not transmit at full power.
All you can do is pick one you like and hope it works...