As long as you’re happy with zwave, the zooz are a very popular choice, have excellent engineering, and the company is committed to trying to keep up with smartthings platform changes, including custom edge drivers to expose advanced features.
If you write to them, you may be able to get a small quantity discount as well.
I agree with your initial feeling: Wi-Fi probably isn’t a good choice for that many dimmers. Z wave, Zigbee, or even thread, would likely be a better protocol choice. (You’d also be pushing it with Lutron Caseta, since it only supports a total of 75 devices per SmartBridge.)
So strictly from a protocol standpoint, I think Z wave is a good match, although the smartthings implementation of Z wave has some significant gaps compared to the competition. 
I am particularly concerned because multiple community members have reported that ST support told them they shouldn’t be running more than 30 or 35 total Z wave devices on a single smartthings/Aeotec hub. The spec itself theoretically tops out at 232 but most certified zwave hubs can handle 150 pretty easily. But there are some “LITE” hubs that only handle 30. I just don’t know why, if that’s true, the smartthings hubs aren’t labeled as lite so that consumers know what they’re getting.