Schiit Freya+ Tube Recommendations

Hello all!...after much consideration - I've settled on a Schiit Freya+ preamplifier. Right out of the box, one tube was bad and caused some awful static in one channel. Luckily, a local friend had a good Tung-Sol tube that I could swap out with the bad one. I've contacted Schiit and am waiting to hear back about getting new tubes.

So, for now I have 3 of the stock JJ 6SN7 tubes, and one Tung-Sol.

First of all, a question for those who own these: Which pair of tubes (left or right) affects the sound more? I'm not sure I exactly understand the function of a cathode follower output stage (left) or differential voltage gain stage (right).

Secondly, my main question: What tubes sound best in the Freya+? At this point - I'm thinking Electro Harmonix or Tung-Sol. But what about NOS Westinghouse, RCA or GE?

I like very clear bass, if that changes any answers...and my speakers are Focal Aria 936

Thanks!