Quality of veg (well, fresh stuff generally) seems to vary with the individual branch, thanks to the vagaries of JIT supply chains. It's the little Tesco that seems best for veg around here, with Sainsbury's doing well for quality but not so good for randomly having empty shelves. Aldi are interesting, because they're good at meat but rather underwhelming for veg. Nearly all of them are terrible for fresh bread in their own unique ways.
I've never known a supermarket that didn't sell large amounts of biscuits or booze. (If we're going to be snobby about junk food snacks can we add crisps? I know they're not very space-efficient, but still...) TBH, as a non-drinker I find the sheer amount of space typically allocated to alcohol baffling[1]. I suppose it has a long shelf life and high margins.
I do reckon Sainsbury's (and Waitrose, obviously) own-brand stuff is generally better than the competition, but the made-up brands of Aldi/Lidl are often pretty good.
[1] Except not really, because you used to get entire shops dedicated to the stuff. Well, you still do, but they're either crap local shops whose main product is booze, or specialist wine merchants.