What does "isomorphic" mean?
Basically it uses a regular pattern of keys, instead of staggering keys into pentatonic and diatonic scales, like a piano does.
This makes it harder to "find" the diatonic scales, but easier to transpose between different keys.
You can see an example here: https://www.youtube.com/shorts/kMD1qXtDAdg
But traditional notation is more compact, and for music based around diatonic scales, implies information about the harmonic function of notes that could be useful for interpretation.
If the key is G you don't start with your hand on C and move it up to G, you start on G and move it relative to that root.
This matters because over/under moves usually happen at certain scale points. So if you learn the scale you have good chance of defaulting to the most efficient movements with muscle memory.
If you're referencing everything to C you'll never understand the scales and their different fingering patterns.
Anyway, here's Martha Argerich playing Prokofiev's Toccata. (What happens around 3:14 may be illegal. But here we are.)
If you watch someone play a Janko keyboard (1) then you'll notice that there is only one fingering pattern for each tonality or chord, you just shift up or down based on the tonic. Kind of like a guitar, where there are a handful of scale/chord/arpeggio shapes that are picked for efficiency (aka, "economy of motion") and aren't tied to the particular key.
It doesn't because it only has a single row of keys. Piano music is full of awkward finger crossings that could be avoided with multiple rows of keys like on the Jankó keyboard.
>or feeling
You can texture or raise/lower the keys on any keyboard as you please. No layout has an advantage here.
>the range for one hand is smaller than the guitar's
True, but the traditional keyboard is even worse.
>there's no bending/sliding/vibrato
Exactly the same as a traditional keyboard.