For this type of programme where you rely on multi-joint (compound) exercises, I'd personally train three times a week and not involve the supplementary (dinosaur) exercises until I could periodise them into the programme when less compound exercises were being used that did not require as much recovery.
Depending on your ability to recover, your nutrition and how hard you were training, doing Squats AND Deadlifts particularly on the same day would be overkill. You can devise a way to train each exercise for 3-4 weeks on the trot with different tempos and total number of reps. Depending on your muscle makeup, doing sets of 6-7 for deadlift and 8-9 for Squats works quite well, but we are all different.
Certainly employing the 20 rep Squat programme is a good idea, but I could only ever do this once a week as it wiped me out. The limiting factor for 20 rep deadlfits is/would be grip and lower back giving out before you'd worked the other muscles over the decided number or reps.