BOSS is the older style of computer management, it's not something you really want. Parts are expensive, avoid it if possible.
BICS is the newer style, it is more reliable.
Traction lock is a safety feature of the computer so it will not move if it doesn't think you are in the machine.
Can't help you on the 7 pin, i don't use any attachments that use it.
I have an S150, it is a very nice machine, it does have a computer, but it does not have hand controls. It makes the potential issues lower as it has no servos to control lift and tilt.