I've agreed to help the girlfriend with hers of going to the gym more
Nice! I suggest doing StrongLifts 5x5... started last February, and really happy with the results
Looks pretty interesting, although this bit could be my downfall.
If you can Squat 140kg/300lb, with your hips going lower than your knees on each rep (parallel), you’re too strong for StrongLifts 5×5.
I used to weightlift with a bodybuilder when I was younger, although I may start off with this to see just how strong I'm not anymore.
I used to do 3x10, so I can see where he comes from, but I wouldn't agree that you lose form on higher reps. If you feel your form going before 10 reps, the weights too heavy. And the whole sore muscles thing is pretty normal. Eventually the soreness stops and you miss it, feels like you didn't train hard enough.