Ubiquiti - Edgerouter X SFP and Aircube AC questions

Xposted from Ubiquity community (not much help so far)

Hey all, I'm a bit of a networking noob so please bear with me.

I have an Edgerouter X SFP, and two Aircube AC units.

My original requirements were simple:

• an affordable router that sits in my data cabinet, connecting to various devices in my house via ethernet
• two or three wifi APs, both powered by ethernet, which will sit on various levels of my house to eliminate wifi deadzones. Bonus: the APs also have their own ethernet ports for other devices to use for a wired connection
• as little config required as possible, hoping for plug and play

I went with the devices listed above because it seemed quite simple. It's been anything but.

Where I'm at now: the internet connection is currently working, for all wired and most wireless devices, via ethernet and the two APs respectively.

Questions:

1. After much googling, I found out that the Aircubes can't be controlled with Unify (control software), they use UNMS. I wasn't aware there are multiple control software apps, or that there was even a difference between the two. Like I said, I'm a noob. Eventually I got my APs recognized in UNMS, which is fine. There's the Android version which is limited in its config options, or the Cloud-based version which I've been using for all the deeper config stuff. Now I've found out that the cloud version is going to kick me out in 30 days, because I have fewer than X devices under management. I can install it locally, but I'm running Windows 10 and there's no Windows client. Is my only alternative to run Linux in a container? Surely not? I mean, I can go to the AP's IP address in my browser and log into it for config, but is that my only option?
2. My Chromecast, which is connected to one of the APs, says it's connected to the network but unreachable. Google's support docs say I need to disable AP isolation, and/or enable UpnP (i.e. Multicast), both in my router. Now, when they say router, I don't know if they mean my literal router (i.e. Edgerouter), or if they're just referring to what they're calling my "Wifi router" (i.e. the AP). Any clues on how I'd go about changing those settings to try and fix it? It's a bit beyond me.
3. I want a single wifi SSID and password for the whole house, regardless of what level you're on, for both radio bands. So to accomplish this, I've manually gone in to each AP's config and set the same SSID and password 4 times (two APs, two bands each). Is that the correct way to go about it? Are they treated as the same network, and the handover should happen if a device physically moves closer to a new AP?
4. Have I essentially bought hardware that is more designed for enterprise, and is beyond the scope of my requirements? I like the idea of a modular system that I can add to and remove from at will.

Sorry for the wall of text.