Squatting with feet together and parallel can be difficult for many people to complete.
Work within ranges where you are able to maintain optimized positioning.
You don’t want to practice compensated positioning.
Optimizing position when you hold on to something to counter balance is key.
Are you able to set up the same as Jstar does in Episode 120: Ten Minute Squat Test #4 ?
You can decrease the amount of assistance while maintaining position.
Shifting weight side to side and knee to ankle as she does will help mobility for feet together squat.
Working on the skill in different ways will help. Incorporate both you mention above focusing on position.
27 Squats with Jami Tikkanen & The M|WOD Coaching Staff
This is a good warm up to working with the squat archetype. It will show you where you are stiff, tight, and warm up the ranges you will be using.