The questions are fine. I never had anyone to ask this stuff to when I started. 🙂
The brake force is a setting for the load cell, it controls how much pressure registers 100% brake force. If you press the settings button on the wheel (the tiny black button on the McLaren GT3) then go one page to the left you can turn it up or down. You can also adjust it in Fanalab.
For cars with no ABS like the F3 and Porsche Cup I set it to 90 or 100% brake force. For cars with ABS I set it to around 60 to 70%, which makes it easier to push the brake down the whole way. In the F3 if you push the brake all the way the wheels will lock, so you need much finer grained control.