Hi there!
I'm planning to purchase the TP-Link Archer A7
(Confused between A7, A6 and C6 Archer Routers)
My question is, how has the experience been so far using OpenWrt on these?
I read some youtube comments on how the A7 frequently disconnects?
I'm a total beginner with this and any tips are welcomed, thanks 
Been using an A7 for some months now... its been pretty solid. I have another C7, and have been using C7's for years... had some issues in recent year or two with problems like that, maybe only caused by certain traffic... the home wifi use has changed with a gamer shifting games/doing less gaming, that and recent releases seem to have made the disconnect problem go away, in at least my case.
I also just use them as dumb AP's rather than doing the routing. You want to consider how fast your net connection is, vs what a C7/A7 can handle, (250-300mbit if no SQM, 100mbit if yes) if it's going to be doing the routing as well as the wifi.