Nice Pendant review here by @grizzlybeast: http://earphiles.org/2019/04/zmf-pendant-review/
Also - as far as tubes, I've found I like the 12au7's the best with ZMF's for more play on the volume knob as the gain is lower. I've been using a NOS Bugle boy and Telefunken diamond 12au7 for a while and like them a lot.
There's tons of EL84's that work great, I recently got a batch of Russian EL84's that sound really nice and clean.
Zach, which set of tubes do you find impacts the sound more? The input 12AXX or the driver EL84s? I believe the 84s are primarily Russian anyway so not surprising that you found some good Russian tubes you liked.