1/ The throttle trim only works if you are in the bottom half of the throttle movement. Try moving the stick to the lowest throttle position, then setting it at 25 so that you can have about 25 steps each way.

2/ The mix is different for each direction. You have to set the mix for both the directions by moving the stick in the direction you want, then setting the mix percentage, before moving it in the other direction to set that mix. It's so you can mix, say, up elevator for both left and right rudder etc.

David C