Although I would prefer you begin with the basic 3day template for a few reasons you could do this 4day template if you wanted to. My reasoning for preferring the 3day first:
1) you're used to BBing training not strength and power training which places entirely different demands on the body. You'll be taxing and working different energy pathways glycolotic vs oxidative metabolism. It's not an either or really of which one you'll work but more shifting the continuum towards one vs the other.
2) when switching from 3day strength training to 4 day it takes a few weeks to adapt to it. Coming from a BBing background you'll be much less adapted even though you're used to 6days lifting. The lifting you've done up until now is different than what you will be doing.
3) doing the basic template will allow you to learn how volume and intensity work together to create progress better. You'll learn the program how it's originally intended which will then help you learn to program your future training.
There are ways to add to the 3day template to get you an extra day but If you want to keep the 4dAy I would
1) add dips to your volume pressing day
2) add rows to your volume pulling and squat day
3) add pullups and chin-ups to intensity pressing day either alternating week to week or adding the alternate one to the intensity squat/pull day.
There are other ways to do this and other lifts you may want to consider but for the first ~4momths or so while you're learning the program and adjusting your body to strength training you'll want to keep the KISS principle in mind.
