it's for the 'pro' models which have a strip of coloured leds that indicate whether things are heating or at temperature.

I suppose there is a plug on the board for the strip. I never bothered looking :-)

There is probably a proper socket for the print cooling fan duct too - as I recall I just wired mine into the same socket as the cooling fan on the board.
Not idea as it meant when the machine was on the fan was always running.
If you find the correct socket you can actually control the fan speed and activation.

I'll have to dig up the pictures of the ightyboard I took and see if I missed a fan socket.
I did the exact same thing on the klic-n-print (creator pro clone).
These days I know better :-)

Yeah the duct is to cool the print area. The existing fans are to stop heat creep.

If you like kapton go for it :-)
Certainly try it before buying anything else.

the machine looks brand new, so probably had very little use.

Basically any different surface you stick on is going to be less than a millimetre thick, so has zero effect on bed temperatures.