I like to set Quaternion rotation mode on all the controls that move on 3 axes (with a few exceptions)
Yes you can get gimbal lock on the Torso, in fact it is really common if the character has to move around the scene in more than 1 main direction. (the issue is when the middle axis rotates near 90 degrees – eg in XYZ, when the Y rotates 90, In ZXY it’s when the X rotates 90 ect)
The torso rotation is kind of like a master rotation for the entire torso whereas the chest/hips and spine are local (if that makes sense)
In game rigs you will find a Torso control (sometimes called COG for centre of gravity) AND a pelvis (or hips) control. This is so the whole torso doesn’t rotate when you need to move just the hips.
If it’s an inplace walk. Animate the root control moving forward then export.
If it’s a translating walk, leave the root alone and just export 1 cycle.
Hope that helps.
