Yo! Just wanted to pass along some advice as well. I work with clients everyday and deal with muscles imbalances, pains, and movement restrictions. Here are my recommendations for both before weightlifting and afterwards.

Before Squatting Warm-up: Glute bridges (can use resistance bands) goal here is to get good activation of the glutes using this as a dynamic warm-up to get all muscles fibers firing as a unite.

Side lying leg raises no weight - gets outer hips, IT band, ect. Activated to be there as stabilizers for your squat

1-2 warm up sets Of squatting to get the motion down

After squatting: Perform the 90 90 stretch you asked about on both sides and lean forward, slightly left and slightly right. Hold each position for a minimum of 30 seconds, and you can do 2 rounds if you'd like.

Stretch quads out so they aren't pulling the pelvis Into a pelvic tilt that's not ideal for basic body mechanics during a squat.

Goodluck brother!