”...splitter to send the signal to FOH...”
Can you clarify what this means to you? X32 and s16 together can have up to 24 physical outputs (16 xlr , 6 aux out and 2 monitor out) plus some other out connections like adat, usb, p16, etc.
But, x32 only has 16 mix groups which I use to create 5 stereo IEM mixes, 4 wedge mixes and 2 effect send mixes. My L and R feed power amps to speakers when we run our own FOH speakers.
If “the signal” is a left and a right to FOH, prob can do without splitter. If it is some number of out and sub mixed outs that combined with your IEM need doesn’t run out of physical outs prob don’t need a splitter. Be advised if you run “direct out” from x32 to physical output it is after the preamp - no way around that I have found.
But if you want a sep. FOH system to control individual channels in the mains, prob need splitter. Lot of flexibility in these digital systems.
We run 24 channels input, and I have the options to run 16 channels to a different FOH board by sub mixing drums to kick, snare, hhat, drum l, drum r. Then the other 11 channels for instruments and voices. I do use 2 art S8 splitters in that setup, with 5 channels coming from x32 for drums and other channels from splitter. I like my eq and effects on the drums.