I'll start with the Candito assertion first. No one will ever add 250 lbs to a REAL max squat in weeks. When looking for advice or programs stay away from youtube lifters like Candito, Izzy, etc. These guys are salesmen, nothing more. Stick to guys like Wendler, Dave Tate, Ched Wesley Smith, Coan, Karwoski, etc.
Twice a week squatting is fine for frequency IMO. Regarding volume, you need to find your sweet spot. You need to use ony the combination of volume and load which permits you to COMPLETELY recover until the next training session. By completely, I mean ONE FULL DAY past where you feel recovered. There is no law that says you need to use a 7 day week. For exampe, I use a nine day week (old fuck at 55). My opinion based upon my 35 years of training experience (17 in competition) is that doubles are only the result of a missed triple.
For the Squat I like reps from 3-6, so one day will be 3 x 3-5 (ramped up sets 20lbs apart) using a modified Hepburn Progression (3,3,3 - 3,3,4 - 3,3,5, etc) followed by one or two sets of 5 second pauses. When I hit 3,3,5 I add ten lbs to the sets and continue. The second day will be somewhat lighter and will follow 3 x 5 jumping in weight only when the heavy day jumps.
Assistance is only good mornings for 3 x 6-10, and leg curls for 3 x 8-12.
When you fail to get 3 x 3 in the Squat, back of 10% and continue. I also don't deload until I feel like crap.