Hey Bart! Glad to have you!
I play guitar, banjo, mandolin, fiddle, and piano; and sing. In other words, I’m in over my head.
I usually aim to practice at least two a day. Practice time for me varies from a few minutes to several hours– sometimes I’ll pick up one, realize it’s not the one I should be practicing, and switch. The next day, that instrument feels like exactly what I want/need to practice.
My practice ratio right now probably goes something like guitar/fiddle/piano/mandolin/banjo. It’s very natural to gravitate towards one the most.
One of the reasons I play guitar the most is because it’s the easiest instrument to sing with. For some reason, it’s also the easiest instrument to connect with (at least for me). I could lock myself in a room and play guitar for hours, but right now I couldn’t do that with mandolin, for instance. That makes me wonder how much I’m biased toward an instrument because I’m better at it.
But practicing any instrument furthers my overall musicianship, because almost all of them lend themselves very well to bluegrass. Most of them really won’t fight each other’s muscle memory, and playing any of them improves dexterity. They all lend a similar overall feeling, but the flavor of that feeling varies between instrument. Guitar is more versatile and complete. Mandolin feels like it requires more precision. Banjo and Violin/fiddle both feel like a specialty/niche instrument. And those are just the bluegrass instruments… Playing piano actually feels very similar to playing banjo, but the stylistic properties are very different.
Moreover, playing different genres on the same instrument is almost like playing a different instrument. Playing jazz guitar is the same kind of technique as bluegrass guitar, but the methods of playing are somewhat different– different enough that playing a jazz song in the mindset of bluegrass can trip you up. Playing a classical piece on violin is much different than improvising on the fiddle for blues or bluegrass, for instance.
From what I’ve experienced, never force yourself to play/practice an instrument. When in doubt, pick the one you’ve been thinking about all day.