That is a good question, and it is quite confusing.
I had 2 sets of #6 Groove tube branded EL84s and both sets were thin and harsh! I couldn't deal with it and ordered some JJs. The JJs look like the identical twin to the Groove tubes construction wise, but were warm and smooth sounding. I bought another amp with JJ EL84s in there and it too sounded great.
Ironically, Groove tubes supposedly screens their tubes and cherry picks the best ones, and that's why the higher price. Are teh Groove to0b people all deaf?
A good way to tell if a El84 is Sovtek is if on the top side of the plates there looks like a frying pan above the gray plates. The JJ's have a halo above these plates. I think the actual name for what I am talking about is the "getter"
Don't know about other tube types though as I don't do this for a living.