Really? I read somewhere that while the C172 G1000 in MSFS doesn’t have aileron or rudder trim - try to find those controls in the plane - you can use the keyboard commands nonetheless, but with my Xbox and a keyboard I’ve tried to trim both, but couldn’t see any movement on either surface or any effect on my plane while in flight. I guess I’ll try it again.
On the topic of AP, it depends. I fly the C172 G1000 almost exclusively, and am still learning. I find AP is very helpful when I’m trying to learn other things, like how to lean the mixture or while exploring the menus on the G1000 NXi. I’ve started a trip where I want to land in and takeoff from every U.S. state and Canadian province (not sure how I’ll do Hawaii yet) and each leg of the trip has a few objectives. The objective on my first leg was to fly AP all the way from West Chicago to Mackinac Island, and it worked great, so I imagine I’ll be using it now and again as I cross the country, especially because I find the little joystick on the Xbox controller tedious to use in cruise and quite treacherous on landing. In short, it’s a tool, and I’ll use it as I need it.