I follow-along with Bill’s advice – center on 3/4", and create a 2nd row on thicker boards. One of the epiphany moments in my biscuit joiner experience is when I realized biscuits do not help align mating boards. I had been relying on the biscuit to provide a smooth surface across the joint, and was frustrated when they’d mismatch. You can get close with creative clamping, but this has nothing to do with the biscuit itself. The Festool Domino is different, in that it does stabilize the alignment; but you need to do a awful lot of joinery to justify one of these…
MJCD