2dof Jazzy Mini [noob]

Wheelchair motors are generally a reliable budget option for most configurations, here is a quick related search of Xsimulator to reassure you of that: https://duckduckgo.com/?q=site:Xsimulator.net+wheelchair+motor&ia=web

I am not sure what you mean by this, can you please explain further.

The motor placement in terms of distance form the pivot increases the inherent design leverage, while the mount point relative to that does affect geometry range outputs.

SimCalc will give you an idea of the tradeoffs, the greater the Y value the more torque efficient, the less attachment from that the more the effect on geometry, but the greater torque required.

In my view it is not the total movement degrees that matters, but rather how fast and accurate the motion is for a given motor/hardware choice.

There are other factors in play that may not be obvious. For example, the closer lower mount point moves the base of the rig, but the effect is multiplied by the height to the head.

This is a game of tradeoffs, depending on maximising given hardware and personal aesthetic/design choices, not one of absolutes.

The greater the distance of the motors from the pivot, and hence the higher the shoulder mount, the less demand on the motors, with some tradeoff of overall movement efficiency.

There are many unknowns, and there is no real 'ideal', as it is a tradeoff, and that is part of the challenge and the fun.

Keep in mind your first rig does not need to be your final one, it can be modified or the hardware can be repurposed. Many of us, including myself, have subsequently made refinements to our original rig, while it takes some work often the related costs are minimal.