I use genalex GZ34. Works perfectly fine.

I’ve used Sivga SV023 with both. Now I am selling Sivga and TA-26, as I use Arya Stealth with TA-20. With SV023 (300 Ohm) TA-26 has more meaty and bloomy, which is fine with jazz and pop, but not very good for fast metal. TA-20 plus have more fast bass and far better soundstage on balanced...

I have TA-26 and TA-20 Plus

Will it work with 274B tube?

Depends on your beliefs.

Right one. Fuse in squared box is spare.

I ordered P26 to accompany my R26, as this is the way in my case to enable NOS and DSD Direct.

The cable is 'cost effective' and universal. You can easily replace it with the one you like.

Had same experience with SMSL D400ES vs D300 respectively. So chosen R26 and like it very much.

Changed cable ASAP. Now i have nice soft cable which doesn't irritate me.

You can't be more wrong. FF3 with Btr5 is meh. Sounds sharp most of the time. With Sony ZX507 it's much better. And with desktop Aune S6 it's sooooooooo much better. It scales very much with better equipment. But sounds quite nice even from phone or apple dongle.