I own the hardcopy of 531 for powerlifting. There's a lot of extra info in there specific to powerlifting vs. the first edition for raw strength.
The only significant change to the "offseason" program is weeks 1 and 2 are flip flopped w/ week 2 being 3x5 for required reps only. Weeks 1 and 3 are required reps only plus a few singles.
I generally start w/ a training max of 90% of my 1RM. I add 5lbs each month for bench/squat/DL instead of 10lbs for squat/DL. I never deload unless I'm feeling beat up. When I do the singles, I generally shoot for speed off the chest, out of the hole or off the floor and keep it 10lbs lighter than the training max. I generally pause the bench on the singles as meet prep and reversal strength.
Bench 1RM - 295
Training max - 265
Week 1 3x3 plus single at 245
Week 2 3x5 required reps only
Week 3 5/3/1 plus single at 255
Week 4 Deload 3x5 (if you need it)
Then the next month I go 270 train max and hit 250 and 260 for singles and so on.
My goal is generally hitting the single w/ speed off the chest. I do lots of downset reps after the work sets. My downsets are mostly for hypertrophy.
The general goal by switching up the weeks is to prevent CNS burnout apparently.
I'm not a big believer in 5 or more reps unless I'm warming up or doing downsets so my version is more like 321 than 531. I like staying fresh and saving the big ones for meets. Something I learned reading Ed Coan's stuff.
I plan on a meet late March so I'll know if this is effective or not by then. But I feel much much stronger using this as each session I feel very refreshed and ready to go by not constantly going too heavy. Being 35 yrs old, I'm finding recovery isn't as graceful as it once was.