I dont think it matters what you have hooked up to your PC as you install LB2. What matters is when you fire up LB2 and its drivers go look on your OS to see what is on the default controller.
Thats when you want just one device hooked up so that LB2 isnt confused.
Back in 1997-1998 when LB2 was new, people really didnt have multiple USB controllers and gaming keyboards and flight controllers that were as complex as we have today.
A single USB or Gameport controller is all that LB2 recognizes, AFAIK.
I can use any ONE of the following on the PC that has LB2 on it:
1. TM Cougar throttle and stick that uses 1 USB port. I use CH Products
Pedal-Pro (gameport) that plug into the TM Cougars, hence still only one USB port is being looked at by LB2.
2. MS Sidewinder ForceFeedBack Pro2 USB. This is an all in one controller that has stick, throttle, rudder (twist), and buttons in one device. Great for travel and laptops.
Now can you have multiple keyboard and gaming board devices along with the single flight controller? Yes.
I use a QUICKSHOT MasterPilot game controller that connects to the keyboard connector and in parallel with the keyboard can give pre programmed game functions mapped to keyboard commands.
On another computer I use a Logitech
G15 which is a keyboard with programmable game funcition mapping also.