Speaking as someone who side steps. It has less to do either power and more to do with body mechanics and having a "plan B" the purpose stepping side ways is to get off centerline so you don't get hit when kicking. There are a lot of other benefits to a side step but that is the main one. Just to step off center to avoid a possible incoming strike.
Side step should be hidden by your attack. Footwork should never be done in a way that tells what attack is coming. Either your step is being done too far away from your opponent or your attack is out of sysnc with your footwork.
A sparring video illustrating your question would be more useful to giving you the answer that best fits what you are experiencing.
Sometime we don't get our self analysis correct because we can't see ourselves in 3rd person while we fight. It's possible that something else is causing your concern that has nothing to do with power.
I totally understand there are many reasons for footwork, and that power isn't all. And if less power is sufficient also wasn't my question.
My question was more specific, perhaps it's best illustrated by focusing only on ushiro geri, or the turning/spinning back kick.
(The application is typically to kick your heel, into the solar plexus of the opponent, or if the right rib side for liver impact depending on your angle.)
I am not talking about ushiro mawashi geri (spinnin hook kick or wheel kick)
the question is: how to make the TURN/SPIN while maintaining balance and not loose power or make it a ushiro mawashi hybrid. The trouble I have is that in a more square stance my center of mass is to the right of the pivoting kick, and if you move your center of mass sideways I think I have to loose energy?
Version one (which i call beginner version) and we are taught at our club this is NOT the way to do, because it's telegraphing. But the power is high.
Another video of same method
This video also lables this a "mistake" (although you can do it for a good reason, but that's a different question, not the one I ask)
Version two, meaning twisting your lead leg, but not MOVING it, supposedly we are taught the better (less telegraphing) but more advanced version. And we are told by instructors this is advanced to execute properly. Sometimes when people do this wither power, they often solve it by a less squared stance, so that the small twist of the leg is sufficient (this works reasonably) But some people do it with a more square stance, and even it can be done, I find that power is lost as your center of gravity necessarily must move during the kick, and howto do that without getting a angular momentum is a bit of a mystery to me.
My instructor told me that the various version may be used depending on circumstances, and this is clear to me. But the question is if the "advanced" version can ever be as powerful? I just want to understand if my hunch is correct, or this impression is all due to my bad technique.