While 50% is 50% and 99.5F is 99.5F regardless of volume, several factors DO impact incubation conditions.
Air flow. With a large amount of fresh air exchange, more water will be taken up to maintain the same humidity. Warm, moist air will exit the incubator and cool, drier air will enter (assuming that you don't live in a tropical climate). Foam incubators, even forced air, do not have as much air exchange as the typical cabinet incubator. I can run my cabinet for months on end and it still smells clean and fresh (I don't hatch in it) yet when I ran foam incubators, I had to let them air out between sets or they'd smell like old socks.
Temperature gradients. In my GQF cabinet, the lowest shelf is the coolest, the upper shelf is the warmest. Relative humidity of the incubator as a whole doesn't vary too much nor does temperature. But locally, there will be a cooler, drier spot in front of the air vent. Temperature gradients in the foam coolers were more dramatic, with as much as 3-4F from the top of the egg to the bottom of the egg.
Condensation. Can be an issue in any incubator, but the more air circulation the less likely it is to happen even at the same average relative humidity. Condensation indicates dead air spots. A little fog in the corners isn't significant, but droplets show humidity is a bit high or room temps are a bit low.
At hatch I drop temp and raise humidity. Temp decrease is only a degree or so, and the humidity increase depends on air circulation. In the cabinet I kick it up with a humidity pad and in the Eco 20 I just add water and a blotter pad to the channels. In the tabletop redwood I needed every sponge I own.
All this says is know your own incubator and the conditions the eggs need for artificial incubation and hatching.
After a few years of practice I get 100% of turkey eggs that make it to day 10 to hatch nearly every set. My challenge has been fertility.