Many with Left side tighter than right?

To answer the 1st Q.
The end goal for most of my clients is to loss body fat, gain lean tissue.
Q 2 - Can it be done without progression to heavier loads v’s doing the exercises in the 1st place at maximal intensity. - Yes it can. However, I test everybody 1 x per month, Body Fat/Lean Tissue.

without doubt, Heavier loads, done correctly, done maximally, in perfect form create a far better response in Fat/lean tissue composition.

Your last part - totally agree. I find most people scale back to mediballs, much like in the videos shown, when their from in Dumbbells drops. Then a week or two, or three later, they are ready to hit the dumbbells again.

Plus there is Variety = less boredom