So maybe I spoke too soon. I've been using the Plugable dual-display adapter connected to the Apple adapter for a couple days now, and I have some updates on expected vs. observed behavior.
My MacBook is set NOT to sleep, but the displays turn off after 5 minutes. After coming back, the internal display does NOT light up as expected, but the external displays do (Monitor > HDMI on Apple adapter, as well as monitor > Plugable adapter). Unplugging the Apple adapter and plugging back in again causes everything to go back to normal. This is keeping in mind that the Plugable adapter is connected to the USB port on the Apple adapter.
Based on what I have experienced in the past, this is new behavior. Typically, when everything comes flooding back at once, things get weird, but it looks like simply unplugging the Apple adapter (and thus the connected Plugable adapter) and plugging it back in sets everything right again. Thankfully, this is a super easy fix, and not really a nuisance since we would have to do this constantly with the Dell docks anyway.
I will most likely be picking up a
Plugable triple-display adapter based on my experience with their other products, and because it seems to strike the best balance between convenience and function. Based on my experience with the Apple adapter, I feel confident that this one will work consistently enough to not be a bother.
Thanks for all your support and hard work! Keep the updates coming