Well, same remark, what to you want?
BIST is Build in self test, means logic added to check macros/logic.
a Bist to check the logic will be memory consumming, because you need to save the stimulus patterns and the result patterns to know if the logic is clean.
BIST is generally associated to memory.
The scan chain number is determined by the number of pads available.
You could also have the scan compression technique, and the tool will indicate the compression ratio usefull for your design.