I know which one it is, but I'm not going to tell you!
You should be able to figure it out once you separate the 2 boards..
Let me guess.... it’s the one with the two marker markings on it because it’s connected straight to the Compressor wire(black) and the heater circuit doesn’t need to use that as it just powers an outlet is all? It’s so stupid that HOT is Blue and COOL is Red...
Well for a start, the way I read the board is, red wire is cool which powers the compressor and fan, blue wire goes to the heating power outlet, the black labeled Com, to me looks like it is "common" and comes direct from the power input lead? and then ACN, which to mee looks to be ac neutral, also from the power input lead.
But without seeing the full pics and or having the unit sitting in front of me, these are just guesses. You need to trace what is connected to where.
Please do that and post a picture or diagram of it.
I don't know that unsticking the relay is a good thing to do, when contacts get bad like that, they can easily burn and cause a fire. If you don't need/use the heater, you could always remove the heater relay and fit it in the cooling position.
As for which relay is which, when you separate the boards and have traced what goes to where, you will know which relay is for cool.