OK, I've been using Unifi for a while now and making it work properly has always been a bit of chore, particularly in managing what channels to put access points as that requires really looking at interference.
But with the latest release, 5.10, this has become much easier:

1. You can't use the square access points anymore, only the circular ones are supported, so if you have some of the AP AC Pro, then you are out of luck, the good news is that five years is quite a lot of service for this stuff, you need to buy the circular ones for them to work.
2. They now have a cloud feature that lets you manage your access points. Unifi is a little different from consumer APs, they require a running Mac, PC or their own little Linux-based controller called Cloud Key. In the old days, there was no way to access something remotely, but now at unifi.ubnt.com, you can manage all the controllers and they even allow remote tunneling via RTC to remote sites. This is really handy if you are going to have to manage your parent's home remotely.
3. Finally, they have an RF Scan and a mesh feature, so if you choose Scan, it will find a place in the spectrum where you have little interference. This gives you a nice graphical way to look at all the overlapping channels, but also it picks the channels that are open.
4. The channel thing is complicated, but basically, there are 11 channels at 2.4GHz, but they really do overlap, so the non-overlapping basic channels are 1, 6 and 11. In the old days, I would eyeball it and have my 1st floor at say 1 and then the second at 6 and so forth, but now the RF Scan can be run to pick the lowest interference frequency allocation. At 40MHz channels, there are even fewer, you have just two channels.
5. Similarly, with 5GHz, there are some channels at 40, then you can bond them together at 80MHz and 160MHz. The thing even supports DFS surveying which means that it sees if there are FAA radars in the way and if there are not will some of those frequencies.

The peculiarities are:

2. The user interface is a bit weird. When you log in to unifi.ubnt.com, you will see all the controllers that it knows about. If you have a Cloud Key, then you click a button at the top that lets you see it automatically. If you are using a Mac or PC, then you have to download the controller software (on a mac, brew cask install ubiquity-unifi-controller) does that automatically if you have Homebrew. Then you have to in that interface tell it your ubnt.com password and that is what hooks it up.