Setting up Raid for the first time

[MorbidNature]

So im thinking of making a raid array to back up my stuff (about 6TB ), but i don't have much experience with raid.

I know what it is and the different variations of it but not how to actually set it up

So a couple of questions

1. Number one or number two - I've got 2 systems - my main PC (Ryzen3600 @4.1GHz with 32GB Ram ) or my "media PC" which is an old PC i salvaged and stuck in a Mini ITX case (i5 3470 with 16gb of RAM). Do you think the old PC can handle it or should i put it in the main PC? Now keep in the old PC still need to work for media playback :)
2. Do I need a raid controller from what iv'e read Windows 10 does have built in raid but im not sure how good it is
3. The actual storage - currently Iv'e got 4 drives, 2 WD Red 3TB, 1 6TB WD Red and 1 6 TB Seagate ironwolf, will the different size drives be an issue?

Also if you have any Youtube videos/tutorials  on how to set it up that would be great

[Electronics Wizardy]

Raid is not a backup, dont use it as one.

 

storage spaces in windows will work fine.

 

It really doesn't need much cpu to make a file server, so your old system will do it fine.

 

Storage spaces allows mixed drive sizes.