Here is a picture that compares the 12.9” Magic Keyboard trackpad with a 2015 MacBook Pro trackpad and an External Magic Trackpad 2. Clearly the trackpad is smaller than most modern Apple trackpads.

I am using the keyboard in my lap now - I am not noticing any issues with the trackpad size, and the keyboard keys are great. It is sturdy in the lap when I put my palms on the keyboard - I am 100% confident in my ability to use this in lap during meetings and conferences (if we ever have those again). However, on the desk, I may actually continue to use the Magic Trackpad 2 because it is so big and comfortable to use (I can also basically use it as a remote trackpad, leaning back in a chair and still manipulating the OS).

I am using the keyboard in my lap now - I am not noticing any issues with the trackpad size, and the keyboard keys are great. It is sturdy in the lap when I put my palms on the keyboard - I am 100% confident in my ability to use this in lap during meetings and conferences (if we ever have those again). However, on the desk, I may actually continue to use the Magic Trackpad 2 because it is so big and comfortable to use (I can also basically use it as a remote trackpad, leaning back in a chair and still manipulating the OS).