The way I understand it, splitting the right shift key requires a different PCB. Are there other differences between the PCB’s?
If not, would I be able to choose “HHKB-Style Split Right Shift and regular 2-unit wide backspace” WITHOUT having to reverse the locations (or sizes) of the caps lock and control keys?
Yes you can do that. There are no other differences in the PCB. All keys can be configured for any key function (e.g. can make the pad caps lock, ctrl, or anything else you’d like). In your case you would order “HHKB-Style Split Right Shift and regular 2-unit wide backspace” and then when you receive the keyboard, you can configure the keys as you’d like. The printed key sets of configured keyboards actually include the original Caps Lock and Ctrl keys so everyone can switch them if they’d like (the HHKB configuration does not take away any keys).