I’m slightly confused by your question. Are you trying to power two thingies off a twofer adapter, or are you trying to multiplex something?
It sounds like you’re just trying to do power so:
See how much each strip draws (either via data sheet of amps per meter times 0.69, or measure it) and if that amount exceeds the capacity of the adapters you want to use, it’ll either not work or shorten the life of the gizmos (or if it’s really cheap crap or you’ve gone way the heck over the capacity of any component it might catch fire a bit).
Note the current on the datasheet wont be linear per length, but for 27” chonks if should be close enough.
Edit: I see now your LEDs are 3V. Personally I’d recommend replacing them with 12 or 24V, or at least 5V to run properly on the 5V thing you’re plugging them into. Why did you go with 3V product?
Wow awesome, thank you for the info and resources! I have to follow the links later but I really appreciate the reply.
I don’t think OP’s strips have pixel control since in my experience you wouldn’t have a separate USB power line that bypasses the controller like OP is describing, but now am curious and hope they follow up.