Newbie question about Vault 2i

I am about to order my new home theater and I am planning on buying Vault2.  I have Ethernet set up in closet where the gear is. 
I am planning on converting my CD’s and also signing on to either Tidal or Qobuz.  
The way I understand it is whatever music I download will be stored on Vault until I drop service.
Vault will be connected to my new receiver.
I will access the music via my iPhone and iPad, correct?
will a subscription to Roon make it easier to use Vault or is the software easy enough to use. What is the Value of using Roon?
Would converting to FLAC be the best option. 
Is connecting to receiver via rca cables to analog out the best way to go
if I didn’t care about converting CD’s would Node 2i be a good option for a lot less money? Is there an advantage to storing Tidal files and Qobuz on on Vault rather than just streaming Tidal to Node 2i.

Bob,  Here are my suggestions/ recommendations:

Any music you either rip from CDs or move to the Vault via your network will be stored on the Vault's 2TB hard drive.

You can load the controlling app (BluOS) on any Apple, Android, or Microsoft device.

I don't stream, so I cannot comment on Roon.  The BluOS app is good but is far from perfect.

When ripping CDs, music will be converted to both FLAC and MP3.  The MP3 files will eventually be deleted unless you tell the Vault to keep both.  FLAC is "higher quality" but will take up more room on the drive.

If you have a high-end receiver with a very good DAC, use a digital cable (Digital Coax or Toslink) to connect to your Receiver.  If not, just utilize the bulit-in DAC on the Vault and use RCA.

Regardless of whether or not you rip CDs, you have to store your music somewhere.  If you don't need the Vault to store your music and are storing it elsewhere on your network, you can just buy the Node instead.

Hope this helps.

Thanks, that was a great explanation. I will be buying Vault 2. Thanks again
I concur with the above.
I have just added Qobuz via the Vault2.  My understanding is that if a download is purchased, then you actually own it, so if you have concerns about losing albums if you discontinue service—or if the label in question severs their tie with Qobuz—that is your option.
Regarding Roon, I would definitely just get familiar with the BluOS app first.  Roon requires a lot of computing power to run, particularly for large collections.  My MacAir couldn’t handle it and crashed repeatedly during the trial.  You may want to ask others how well Roon operates on a Vault before you do a free trial.
Regarding which DAC to use—the AVR, or the Vault2–it depends on your gear.  The DAC in the Vault2 is ok, and will play MQA via Tidal, if that is important, but isn’t the last word in refinement.  If you have a better DAC in your AVR then go that route.  You should be able to do both—connect to your AVR with analog and digital cables—and then easily flip back and forth using the AVR remote and compare
I was all set for Vault 2 but after considering all the money I will be spending on Home Theater I think I will just spend $500 on Node 2i. My reasoning is that I can live with the conversions of my CD's to AIFF that I have done. Unless I am missing something I don't see why I need HD of Vault as I won't be purchasing music. I think for streaming Qobuz, the Node2i will be fine. I may be wrong on this. I know Tim said I have to store music somewhere but my nephew who uses Tidal said streaming is not a problem and he does not store the music on HD. As far as my converted Aiff files they are now in my iTunes folder. Wouldn't the Node 2i be able to access this.
I don't have any plan as of now of adding Roon. Thanks
@galleybob - If your AIFF files are on a system that is attached to the same network as the Node2i, the Node should find them. I don't own one, but I own another streamer and that is how it works. It will catalog every audio file it finds on the network.

Hopefully a Node 2/2i owner will chime in and validate my assumption.