If I am remembering this correctly, that shouldnt affect any existing sims either until you bring them into CAS because then at that point their sliders will adjust to be within the new range (even if you werent planning to change anything slider-related in that CAS session). If you adjust the slider ranges to be more restricted, then some sims may end up with slider values outside of the newly defined ranges.
The MC Integration add-on module will extend the MC version of CAS to the built-in game ones (except for when CAH is jumped into at the very start of a game session because in that case the mod will not have had a chance to finish loading).
These MC settings will only apply when in an MC command called version of CAS, not in EAs version. Note there is a similar option for Slider Multiple:Body, but a Core Mod such as the one by Consort at MTS is required to prevent sims from snapping back to within range during gameplay on the weight and fitness sliders. The default is 1, so changing that to 2 will extend the slider to 2x maximum in both directions.
