Yeah, I thought about using the separate pixel controller for the lightboard project later. (As I said, I have dreams - I want to get some plywood, paint it matte black, run led strips on it and cover with sheer nylon fabric for light installations.) DMXKing has a pretty nice solution for this, allowing up to four strips to be connected to one pixel controller. This would work for that solution because it'd still be self-contained. (Edit: It looks like the Startimes LED controller you linked to is pretty similar to the DMXKing box I found.)

I didn't want to do the separate PSU/controller mainly because of the wiring issue you mentioned - having to run cable to the strip itself. It would limit the options due to cable run length, and I don't think it'd be the optimal solution for something plug-and-play. Because they wouldn't be self-contained, it also wouldn't scale as well if I wanted to start making more standalone versions. If it's the only workable solution aside from having to program an arduino nano, though, then I might have to do it.

I was hoping to find something more like this (https://www.amazon.com/TORCHSTAR-Channel-Effective-Converter-Constant/dp/B075XH7FDG/ref=pd_rhf_dp_p_img_3?_encoding=UTF8&refRID=FQV0M90654Q4K0GWT5QA&th=1) but specifically for pixel control. While this wouldn't fit inside the c-channel, it could probably mount to the outside along with the power block, or I could figure something else out. If anyone knows of DMX pixel controllers with this form factor (ethernet support as well), I'd be interested.