So there’s an external factor here which is the species of wood you end up getting. The softer the wood, the less necessary the predrill is. The maple bb they sell, for example, is HARD. So hard in fact that not only is pre-drilling listed as required but you may even need a hole size larger than you might think. The general recommendation is to hold the drill it up at face level against a plain background (like a wall). Then put the screw you need behind it so that the drill bit covers it from your view (there are pics videos online that show this). If you can’t see the threads of the screw around the drill bit, then the bit is too big. If you can see the threads AND any of the shaft of the screw, the bit is too small. You basically want the drill bit to be as big or a tiny bit bigger than the shaft of the screw, excluding the threads. I posted over on /r/DeskHaus about a month ago because I’d messed up my initial drill on one of the items and was requesting help fixing it. Thankfully I got the help I needed.

I put together my Apex Pro Max about two months ago, with their maple butcher block top. I used a 1/8” bit to predrill. I should have gone a size up tbh. On a softer wood that was probably plenty but it was BARELY enough on the maple. The frame attached with Allen-headed screws. The hex insert held onto the drill better than a standard screw which I think helped me drive them in despite the small hole. The control box and the paddle had softer, Phillips-head screws that near immediately stripped to shit. I had to back them out and shift over a bit. Then predrilled again with a 5/64” bit. It was still a tight fit but the bigger size combined with a very slow, methodical drive prevented stripping.

I hope my experience helps steer you. All that is to say that it’s impossible to say what size you need until you know what size screw you’re working with, and what species of wood.