Ah yes, depending on how you've started a printer profile in Cura it may include some speed limiting commands for marlin based printers. Best to delete those lines.
I think the PETG available today is generally as easy to print as PLA. Hotter temps and less cooling are the big differences. Otherwise most print settings can remain the same.
are the idlers toothed? the original idlers on the ender 3 are large so non tooth is ok.
but if you went with 16t pulley you might have gone with smaller idlers.