So, I’m a bit late to the party, but I waited for the VR update and today Santa gave me a user license for MSFS2020! 
So I went about installing it. When first selecting which drive to install to, at the Microsoft store, I chose my E: drive. That didn’t take long.
When starting MSFS the first time it says it needs to update…and suggests the C: drive, under the User library…
Are they serious? Does it have to be on the C: drive, since they want to put it under User?
I’d suggest making a MSFS2020 folder on your E Drive and point the installation there. 
Doing this makes finding your community folder very easy, and places the folder in a non-protected area. Having the community folder buried in the Windows rabbit warren of folders is a real PITA…ask me how I know! 
I gave it a whole SSD drive. 
But yeah default is C: which I cannot recommend.
Ok, so I can change the default location…
I kind of thought I did that, by selecting E: when I chose install in the MS store… But it still promted me to install the updates in C: 
So… I stopped the install, uninstalled and started a new install on E:MSFS2020 this time around.
Thing is, when I started the first install, it said some 128Gb needed to be downloaded.
Then it installed for a few Gb before I stopped, moved and restarted.
Now it says 121Gb…?
Will I now have a split install…? I reeeally don’t understand this installer.
The store (or Steam or whatever you got it from) will install about 1GB. This is the installer and all the crap MSFS needs to work. Frameworks and such. It does not really matter where you put it as it’s not much (by modern standards).
Once this is done you run it and it will get all the bulky game data. This is where you need to pick the destination carefully. Your Community folder will be in the same place. In your case E:\MSFS2020\ or similar.
I’ve only done this once and forgot the details. But understanding the concept might help.
Then once in game you can choose where the scenery cache is supposed to be. Plan to have 20 to 40 GB for that in an independent location.
Had to stop the download yesterday as I am not allowed to have my PC running when we sleep. Not since it became common household knowledge that it needs liquid cooling…
Restarted the download today and it seems to have picked up where it left…
Yeah that works fine, I also paused mine a few times.