Other than a few unique backplates (DSS, Oxycheq Ultra Lite, Freedom Plate ....), in most cases, a backplate is a backplate is a backplate.
If you want to dive a single tank without a STA - then you have to be sure that the slots in the plate match the slots in the wing. If you are using a STA - you can mix and match, however you want. The differences are minor - some hold the tank closer to your back, some have more radiused corners, some are shorter - but in the overall performance, most people can't tell the difference.