The high pitch Ooh vocals sound great, I'm guessing those are pitched up a bit with melodyne? actually sounds like a female vocalist at parts.
For a so called "experimentation" this is really great, I enjoyed it a lot.
Coming from Cubase to Reaper, I found Julian Sader's multi tool script a godsend for the midi editing, as that gives some of the same functionality for editing CC values (scaling, cresc, decresc etc.) that Cubase has + it also works outside of the piano roll in the automation lanes too! Might be a good thing to try out?
https://forums.cockos.com/showthread.php?p=2211574/1000
Also, adding some actions like enabling/disabling multi track editing etc to the key editor toolbar helped me a a lot with making working in the key editor more smoother like in Cubase.