I understand if this seems tongue-in-cheeck/sarcastic, but it's not intended to be: if at all possible, get off the airwaves and use wired connections, at least for important and for static, non-mobile connections. You will have so much less issues it will only deepen your hatred of WiFi performance.
I tried for over a year to "engineer" a home WiFi setup that wasn't worthless. Several upgraded wireless routers, changing locations inside the house, installing a repeater upstairs, etc. Things that seemed to work initially, like installing a new "better" wireless router, would eventually, sometimes quickly deteriorate back to initial poor performance. Sometimes I swear my laptop sees various neighbors' WiFi signals at higher strength than the router in the adjacent room.
Eventually I got sick of it and just laid Ethernet cable across the floor from the router to my main machine, very ugly, and all the problems were gone (duh, right). But the performance difference was so staggering that I instantly no longer cared about "ugly" wires, because one solution worked and the other obviously did not. Since then I have used various trim products to hide the wires without routing through the walls (I don't own the home so I have to get creative), and now the only wireless devices are tablets and phones and if someone insists on not being near one of the many Ethernet ports in the house, a laptop.
So, I know this is borderline off topic because it is not a wireless solution, but I sympathize with the problem and say, "Good luck." I couldn't solve it satisfactorily, and eventually turned back to cabling.