I ride in the very hot, humid south. And the cotton pad, with a wookbak, then a gel pad on top. You have to make sure it doesn’t displace the saddle and make it not fit. Like I said I just play it by ear, and I can mix it up. The thin cotton pads keep the woolbak cleaner. Woolbak will absorb the heat and sweat from the gel pad. Also I can switch the pads and use clean ones. I make sure all the cotton pads have a lift in the front, and I do pull the pads up and into the saddle so it doesn’t get too flat on the back.
There is alot of sweat going on, and the cotton pads are nice to have, but you can just use the woolbak all by itself with the gel pad. I put the pad next to the saddle, and not on the actual back of the horse, so the heat is less, or not a factor.
I have ridden english since I first started to ride, long long long ago. I think it is the best fit for the horse due to the saddle being able to be custom stuffed.
The cotton pads are not that expensive. So I have several, different colors so I can keep track of which one is dirty or clean or was used last on what horse. The do not have to be washed each time. I like clean pads though, so I keep mine pretty well washed, since they get nasty usually. After a ride here, everything is sweaty and very nasty. I like to switch them out at vet checks. Well for that matter, even in competition on a LD I try to change all my clothes at the vet checks. I for sure switch everything during a 50 also. I think the horses like a fresh clean dry pad, me dry clothes. Even my gloves if it is that hot outside.
I think my gel pad is a roma gel. Not a total down the side type gel pad. Not very expensive. Nice, easy, does its job.