Pumpkin waffle batter is dense, so whipped egg whites are used to lighten the texture and provide some loft beyond what’s achieved by the addition of baking soda/powder.
The ideal is to whip the whites to the stiff peak stage. That allows them to be firm enough to withstand incorporation into the batter. But getting them to the perfect point can be a challenge, as there’s a delicate balance between the stiff peak stage and whites that begin to curdle. So as soon as you begin to get glossy undulating waves and ripples in your whites, it’s time to pull the beater(s) out. Check out the photo below for a good visual of how far I take the beating, or check out this egg white whipping video for a great lesson on how to whip to perfection.
And, once you start working the whipped whites into the batter, it’s crucial to carefully fold them in. Stirring would quickly crush their air pockets, so you want to slowly scoop from the bottom of the batter and fold that batter over the top of the whites. The final batter is ready when no white bits are obvious. If you continue to mix beyond that point, you’re only going to make the waffles progressively tougher and more dense.