Y will not work at all, it will cause a lot of issues.
For wireless DMX transmitters, look
here.
For the transmitters, you can only use the 5 pin or 3 pin, not both at the same time. This is the same with fixtures that have both 5 pin and 3 pin, its one or the other. For the splitter, you can use both 5 and 3 pin outputs at the same time on the Elation units. Each bank is like a separate universe. You can not, however, use the 5 pin and 3 pin input at the same time and the 5 pin and 3 pin pass thru at the same time. You can, however, use it as a turn around, going from 5 pin in to 3 pin thru and visa versa, same with fixtures as well as the wireless transmitter.
You can also turn 5 pin into 3 pin and back again as many times as needed. 5 pin DMX only uses 3 wires, the others are there for expansion which never really happened.