combining them can be annoying
The strong design opinions about how the Pocket Operators interact with other musical gear are a big part of why I haven’t had high enthusiasm for using the small PO’s when I’ve had small PO’s.
For me, Volca’s are a similar ecosystem but to a lesser extent…maybe because the Monotrons sit lower in Korg’s product portfolio while the PO’s are rock bottom of TE’s product line.
I gave my kids (5 and 2) two Volcas (Beats & Keys) to play with. The Keys is a bit too advanced (too easy to get no sound at all, or something that sounds horrible), but the Beats is a wonderful machine for kids, as it's virtually impossible to make it sound bad. Also great to teach them rhythm.