I have both.
I must delete the BlueTooth model to control the new WiFi-only device, and vice versa.
It appears, with the current App, that you can control only one unit at a time (from a given device. I’ve not yet tried using my old iPhone 4 to control a second unit.)
I have no experience with attempting to control multiple WiFi units simultaneously; I would hope the software team is working on this in advance of their hinted/promoted Steam Oven.