MRTK's Solver documentation says that you can "stack" solvers on the same object and their effects become cumulative.
The Known Issues section implies that you can control which order the solvers are evaluated in, and that this can cause differences in behavior.
How do I change the evaluation order for two solvers on the same GameObject?
They update in the order they appear on the game object in the inspector, top to bottom (as long as GetComponents continues to return them in that order!) You can rearrange component order by clicking the gear icon for a component in the inspector, and choosing 'Move Up' or 'Move Down'. Hope this helps!