I am a big fan of Ubiquiti. I live in an 1850s farmhouse that has a tremendous number of nails in the walls on the first floor, so Wi-Fi waves don't penetrate well. On top of that, when they worked on the wall between the kitchen and the wood shed they put a layer of metal foil in so that the penetration through that wall is close to zero. We also have an armoire with a mirrored back that blocks waves from the rest of the house.

We have 4 access points.

In summer we move an access point from the kitchen to the woodshed (with a powerline internet adapter). Tablets work in the kitchen but it would be ideal if we added one more access point to the bedroom above the kitchen.

It's no accident that Apple is not making a WiFi access point because "just works" is an impossibility. If you believe in the apple aesthetic you probably also feel entitled to install your access point at whatever corner of the house your cable box is installed, despite what physics has to say about it.

The awful truth is that different WiFi chipsets are just barely compatible with each other, high-end access points are chock full of workarounds for flaws in WiFi clients, and companies like Cisco and Ubiquiti have lots of patents on those workarounds. They have a "mutual assured destruction" policy that they don't sue each other, but they make sure that routers from companies like ASUS work only occasionally.

Powerline internet adapters are your friends. Their weakness, relative to modern switched ethernet, is that all the devices share a common bus. For best performance, use just two powerline adapters to make a "point-to-point" link to support one far-flung location.