Can I raid 0 an older HDD with a newer version?

Solution
RAID 0:
The speed of the slowest, and 2x the size of the smallest

A slow drive and a fast drive = a slow RAID
1TB drive + 2TB drive = 2TB RAID 0
1TB drive + 1TB drive = 2TB RAID 0

Additionally, you are introducing much more fail potential.

Just add the new drive as a new drive letter.
RAID 0:
The speed of the slowest, and 2x the size of the smallest

A slow drive and a fast drive = a slow RAID
1TB drive + 2TB drive = 2TB RAID 0
1TB drive + 1TB drive = 2TB RAID 0

Additionally, you are introducing much more fail potential.

Just add the new drive as a new drive letter.
 
Solution
Is there a difference in the speed between the two? And also doesn't the speed get bumped up?
Also I'd rather do raid 0 so I don't have to deal with 3 different drives every time I install something and I've never had a drive failure in the past 15 years I've been around computers so I'm fine with that.