That is already doable with xargs itself

xargs -P maxprocs

Parallel mode: run at most maxprocs invocations of utility at once. If maxprocs is set to 0, xargs will run as many processes as possible.

if have 10 computers put every 10th line in its own file, if each file is 1000 lines put line 500 at the start, then line 250, then line 750, then line 125, 375 etc