The Importance of Posture by: Batman from Isometric Training
That's a very good question and the answer is yes, to both.
It is very much dependant on how you train and the nature and severity of scoliosis. Of course, as a usual disclaimer, my programs are not designed to treat or remedy any medical conditions.
That said, I work in the field of spinal diagnosis and repair (and my Isometric methods were even featured in "Spine" a Medical Journal for spinal specialists).
It goes without saying that any form of exercise, including isometrics, can be both beneficial and detrimental to our physical health.
If you for instance focus on the "mirror muscles" chest, biceps, abs" etc and neglect training your back muscles, your chest, biceps, and abs will all get bigger, and rounder and pull your back out of alignment. The classic muscle-bound look. Not good, particularly if you already have scoliosis.
By contrast, if you focus on unilateral isolation isometrics connecting to the areas of imbalance in the spine, then you can strengthen and tighten those muscle's improving posture and reducing spinal curves. Exercises like this are a vital part of the treatments I provide in my clinic when dealing with patients suffering from scoliosis.
For more on posture and specific treatment plans for a range of spinal imbalances check out Samurai Strength Vol. 13 - The Warrior's Guide to Perfect Posture - available here - https://samuraistrengthtraining.com/
This covers the 10 most common postural deviations, how to spot them, and most importantly detailed guides on how to correct them through a series of 20 specific posture enhancing and back pain-relieving stretches and over a dozen targeted exercises.