X rotation stretches my clip

You may want to start by reading the online help on all that 3D stuff. A custom view is not the one that will be rendered, anyway, so you're basically workingf blind.  The rest is normal behavior. There is no stretching, it's just the normal camera lens distortion. If you haven't created an actual camera layer this will be based on the imaginary default comp camera which uses the last active settings when a camera layer was created. So start by creating an actual camera and check its properties for focal length, film back and so on. All this affects the projection. Yours uses an extremly short lens, so the distortion is strong. Longer lenses have less distoertion.

https://helpx.adobe.com/after-effects/using/cameras-lights-points-interest.html

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