I pretty much (finally) got an MIDI only Orchestra Song from Cakewalk by Bandlab converted to Studio One (via ReaCWP and Project Converter).
It required some manipulation after these steps:
1. Consolidate all MIDI tracks (not 100% sure this is necessary but a 'safety' step' Save song as well as Fabfilter C 2 VST3 settings as a preset (more on this later).
2. Open Reaper (with ReaCWP plugin installed) and open the Cakewlak project(.cwp), Save as a Reaper .rpp file. The piece plays just about how I expected it to.
3. Open Project Converter (v1.2.2) and convert the saved .rpp in step 2 to a DAWProject file.
4. Open Studio One and open the DAWProject file.
Now here is where the fun started.
1. Project tempo was off (120, not 90) and the MIDI performed as such (too fast). This is probably moss's issue, but maybe not? So, I went back to Cakewalk and saved the project in MIDI 1 format.
2. Removed all MIDI in Studio one and replaced it with the output of the MIDI 1 saved file. Just FYI.
3. Now the DAWProject file seemed to think that Kontakt and Opus were audio FXs not instruments (unzipped DAWProject file and confirmed). So, it created audio tracks with Kontakt and Opus as 'inserts'. Studio One has an Instrument Rack and then uses instrument tracks feed their MIDI data to the respective instrument in the rack.
The conversion did create instruments tracks with the MIDI correctly. But they had no "instrument" to point to. Is this due to how you stored the VSTi's in the .rpp file?
Nothing played.
This mishap is on Instruments that either you or moss need to solved. Please verify that.
Small issue is that although FabFilter C-2 (VST3) was in the Reaper project on one instance of Kontakt (since it was in the Cakewalk project). The guts of the DAWProject file created by Project Converter knew about it. Studio one did not have Fabfiler C-2 VST3 in it (nor the VST version either).
But here's the weird part. All instances of Kontakt and Opus do a send to EW Spaces II. Spaces II is in the .rpp and DAWproject files. And it's in Studio One after opening the DAWProject file with the correct settings (on an audio track).
That too needs to be solved probably by moss unless there is something different on how you store FabFilter C-2 vs EW Spaces II in the .rpp file.
=== FYI about Studio One ===
Fortunately, the inserts of Kontakt and Opus (11 in all) were configured correctly. So, I simply dragged them to the instrument Rack and then pointed the instruments tracks to their correct instance of Kontakt and/or Opus.
Then I added Fabfilter C-2 VST3 and loaded the saved preset made back in Cakewalk.
The project plays "pretty much like the original Cakewalk. I did not do a null test. I'd expect them to probably not null but I'd rather just trust my ears that it's good enough to start with if I were inclined to either edit/add to/remix the orchestra piece.
Knowing what I know now, it would take about an hour or so to do similar sized projects. But if the VST3 (Fabfilter C-2) and the Instrument Rack (Kontakt 7 and Opus) were solved it should take considerably less time and be less prone to human error I took in the steps above.
=== end of Studio One info ===
If you need to see the guts of the DAWProject file, you can rename it to add .zip and open it to see/read the xml file that describes all the contents that Studio One/Bitwig uses.
Lastly, I've included a DAWProject file created from the "fixed up" version of the Studio One project for reference. I appreciate that Project Converter is not your responsibility, but I wanted to provide you with all the information about Studio One I could.
FYI Bitwig suffers the same issues that Studio One does except it does set the bpm to 90 and the MIDI looks to be correct, but I did not go through all the steps to get it work there as I only use Bitwig for educational purposes at this point, but if the Instruments get sorted out, I could confirm that the MIDI is correct.
Once again, as I've said in the past, I would be happy to donate a copy of Studio One Pro license or a year of the new subscription to you to help sort out where the disconnect lies in the FabFilter C-2 and Instruments Rack issues I've outlined.
Here are the relevant files:
https://www.dropbox.com/scl/fi/eiu9lvxv2qlfa9ertg6xh/ReaCWP_ProjectConverter_Examples.zip?rlkey=f31toyyguxndcgbaus63uwyk5&dl=0