Would removing spacers increase the power transfer of my pedal stroke since I'm in a lower position and activate the glutes more?
Overall does it increase or decrease it?

Position certainly makes a difference. Different people climb best with different positions. A trad climbing position is hands on bar tops, forearms almost level, back straight. You can do that with whatever bar height. So if you're already climbing like that, sure pull some spacers and see. Only takes 5 minutes to move the spacers. If you're using that position, try it.