not a lot left that you can change.
It's unlikely to be the LCD or the hard drive.
The processor will have had new thermal paste when the logic board was changed out, but that does not rule out failing fans.

Had you not mentioned that the board had been changed out, I would have gone with it as that is where the graphic card is.

If the MBP is under warranty, back to the shop it goes until it is either fixed correctly or it's replaced