You basically clamp the UCA and LCA in that position when you torque them. Think about it, to remove the factory coil over assembly it is much easier to loosen the LCA bolts so that it will drop more. These are not bearings. You absolutely torque the bolts on the control arms when the suspension is loaded.
And yes cutting the springs does increase the spring rate:
https://www.eatondetroitspring.com/cutting-coil-springs/
And if you want the math behind it here you go:
https://www.eatondetroitspring.com/cutting-coil-springs-calculations/
Also, when you cut a spring you need to understand that the factory dampers were designed with a specific spring rate. Now that you have cut the spring you may very well have screwed up the damper/spring combo. If you are going to tinker with spring rates you need to understand how this will affect the damper or have the $$$ to get adjustable dampers. Even then you can get crazy and get custom valved dampers so you can mess with different spring rates but that is usually on race cars. Think Penske here:
https://www.penskeshocks.com/