Spent a bit going thru the PDF for Real Flight 9 and nothing I came across about changing rates or and fancy things like pid changes.
What I see so far is you are a little over your abilities with your rates. If this were a real quad I would say cut back the Rate and up the RC Rate to return the over all DPS to where you were at on roll channel. That would give you the same roll rates but would be like adding expo (which for quads adding expo should NEVER be done) Same for other channels but not as much as you were not over shooting and wobbly on those axis as much.
From what I read I think RF 9 multi rotor section was just an after thought with no real effort. I think what they did was re-skin a plane and manipulate the physics parameters to emulate a multi rotor. I did the same thing in Reflex XTR since it was made long before multi-rotors were a thing. Thats how I can recognize the behavior.
If you really want to get better with quads on a sim format I suggest one of the dedicated FPV sims. I like the physics of FPV freerider best but Lift off and Hot Props have more realistic settings emulating beta-flight so you could actually learn more what things do in real world set ups. DRL is too cartoony and the physics are really bad last time I messed with it. Not sure about the DCL game FT just got involved in so I cant say but it also looks cartoony to me.
Just be aware that every mutli rotor sim out there seems to set gravity a tad light so everything feels to floaty. Its better to go heavier on gravity and adjust free fall and flight with the weight and power portions of settings.