We run via RDP too. And printing (even with a great connection) is abysmal.
I’ve been told it comes from the Client server (the one running the Epicor client program) querying the RDP client (the users computer), to see what printers are available.
The first (and currently used solution) is to just print preview everything, then print from the PDF viewer. But know that this is probably bad for printing tightly formatted things like labels.
It might help for direct printing, to trim down the number of avaialable printers on the RDP client. That way there’ll be less back and forth between the RDP client and the App Client, while they negotiate available printers.