Apple cluster control means running many iPhones from one computer: screens viewed together, tasks dispatched by group, results collected in one place.
This one answers: How Do You Lay Out a Rack for Apple Cluster Control.
Xu used to run four phones on his dining table, cables tangled in a pile.
This year he rented a ten-square-metre room, moved the gear over, and lined twenty phones up in a row. They looked tidy. Then he sat down, stared at them, and messaged me: should I buy boards?
I asked whether the phones would ever be picked up and moved. He said no, they just sit there.
Then not yet.
One question decides it: do you have a distance problem
Everything about choosing a link comes down to a single variable.
If the phones sit on a rack and never move, a data cable is enough，USB HID. Console 10.7.0 or newer, phones on iOS 17 or newer, one cable per phone into the PC. No Bluetooth board, no OTG board, no proxy IPA, no signing.
If phones get picked up and moved, or are spread across a few desks on one floor, WiFi is simpler.
Boards only come in when the cable genuinely cannot reach or you want it gone: Bluetooth uses an ESP32C3 board, and its absolute-coordinate firmware behaves well on iOS 17 and up; OTG uses an ESP32S3 board and supports iOS 17 and above only.
The question is not which link is faster. It is whether you have a distance problem.
Cables are a bigger trap than boards
The first night after moving in, Xu called to say only eleven of the twenty phones showed up.
I told him to take a cable that had not been recognised and plug it into a phone that had been. He went quiet.
Charge-only and data cables look identical, sometimes down to the packaging, and cost half as much. The cheap ones are missing the data cores entirely. The phone charges fine; the computer sees nothing. You cannot tell by looking.
Buy the rack cables in one batch from the same model, and do not mix. Cables also fail over time, especially at the connector where they get plugged and unplugged daily. The test is simple: plug it into a phone you know works, and if nothing appears, it is the cable.
Placement, power, heat
With twenty phones online, the first thing to break is not software. It is power.
Xu started with one large USB hub, a single cable to the PC, twenty phones hanging off it. Fine for two weeks. From the third week, three or four phones dropped at random every day, a different set each time. He measured it and found the hub had no independent power supply，it was running twenty phones off one PC port.
Two powered hubs, devices split across different USB controllers, and the dropouts stopped.
Do not skip cooling. Twenty phones packed together get hot enough to burn your hand in summer, and the hot ones throttle first. Leave gaps in the rack instead of stacking.
One small habit is worth adopting: name every device with what it does, so the console shows something better than a row of numbers. Xu uses platform, content direction and a number. He reckons it saves him a few minutes every day.
When wireless actually earns its place
Xu never switched. Two situations would change my advice.
One is when devices spread out. Ten square metres holds twenty phones; fifty across two rooms means a real distance problem, and that is when WiFi or a Bluetooth board starts to make sense.
The other is running two PCs for different groups of phones, where the cabling gets awkward and wireless is cleaner.
If the motivation is simply that wireless sounds more advanced, it is not worth it. Boards fail, firmware needs flashing, and once pairing is involved a problem means checking three places instead of two. Those costs do not show up immediately, but they show up across a year.