Your drum replacement approach with GAse?

Hello cubasers I’d like to know what is your approach with GAse when blending/replacing drums.

Say we have a classic rock song and we want to improve its drums.
I usually set the velocity all the way up and flat because I find the dynamic velocity very hard to control, but I am interested to hear your philosophy on that.
Do you usually set the Velocity or the Layered mode? How do you shape your velocity (on the midi file?). How many layers?
Thank you.

In addiction, I’d like to understand what the poly function do. I read the manual but I need a real example to understand it really. Am I missing something special here?