Here are the mods I did in the order I did them for my 2018 RC:
-Emptied the cat/ removed the baffle (stock exhaust)
-Power tronic ECU (or in your case the power Commander)
-Open airbox mod and k&n filter
-Oversized fuel injector
-Dyno tune
Full exhaust systems are pretty expensive and...
I installed the oversized injector and didn't get it tuned until a few weeks afterwards. The ecu seemed to do an alright job dealing with the injector, I would definitely get it tuned sooner rather than later if you put the injector in. my local tuner said he was surprised with how well the ecu...
I emailed Rok back in August 2019 and was told that they'd have it back in stock January 2020. That never happened so I wouldn't keep your hopes up.
I'm sure if we could gather enough people we could probably do some sort of group order before then.