The only time I use 2.1mm is when I'm going to daisy chain or do something besides point to point, when I'm doing solar, or when I'm using the connector for something other than power(A voltage divider can protect your input from accidental power connection, so it's one of my favorite simple connectors).
Just watch out, 12v isn't a thing anymore in the new specs and might not work, best to build around 5v, 9v, 15v, or 20v.
Although usually if I just need 5v, I'm building around a D1 Mini ESP32 module that already has 5v built in.
Edit: the one chx linked to above is precisely of this kind
Fairly cheap but easy to configure with the dip switches and the boards I've been sent have been high quality with good solder joints.