I'm currently using the Planck and have been using Dvorak for years
The Planck comes pre-loaded with the Dvorak language as a layer by default when using the single, 2u spacebar layout
I'm looking to get a Preonic because of the slight hassle of typing numbers by holding down the layer up key to type numbers
my actual keys are in the QWERTY layout but it would be simple enough to just swap them around, though the apostrophe key and the forward slash key would be the wrong colors based on their placements.
I personally have found that having an ortho layout has been super nice, except that hitting the c key (j in dvorak) with my index finger has been a bit of an annoyance, but that's a habit I've been pushing out of my typing habits, albeit slowly
I will say, I'm EXTREMELY new to the keeb world so my experience with keyboards in general isn't super extensive so take my praises and qualms with a grain of salt