You have to go into 531 understanding that it's not as strict.
You 5x10 sets can be from 50% to 70% of your training max. Your training max is the number that you use for each cycle to base all your working sets off of, and is to be adjusted as needed.
He recommends going conservative with it to start.
So if you are having trouble getting through your 5x10 at 60% with deadlifts, but squats are fine, you might drop deadlifts to 50% instead. The idea being that your volume work is good reps with good bar speed.
Doing 5x5 then trying for another 5x10 will be brutal, there is a single topset each week with 531, and there are options for additional heavy sets, but they are excluded from BBB. You do your top set, you do your 5x10 work, then you do any assistance work you think you need on top of that and you get out.
I would always just do something like rows with the same weight as bench, pullups opposite of overhead press, and core work with deadlifts and squats while doing the 5x10. It goes relatively quick.