Cockapoos aren't a mix I'd go for myself either, as I think I said earlier. Oddly, as I realise they're probably the most common, they're not a mix I encounter much on my walks. There is one actually, which looks pretty much like a pure cocker and runs rings round the older lady who owns it, but it's only 6 months old. I did cringe a bit about her choice 🙈
Retriever/poodle mixes I have mainly on my groups and they all seem to be pretty much problem free dogs after the puppy stage. Size can be an issue ie a 'mini' ends up to be not so, but nobody seems to mind, bar one poster I remember a few years back who asked if they could sue the breeder for the extra costs involved with raising a larger dog... but that's FB for you 😂 It's also quite telling that many go on to have a second and more of those mixes.
In my area the smaller poodle crosses are most common, mixed with ckc, bichon, shih-tzu, Maltese. Some are yappy, but I think that's often common with mini poodles and those breeds, apart from the ckc anyway, but otherwise they're sweet, friendly little things.
My dog, GR/lab/poodle, is exactly as you describe the dog you're sitting for, as are the rest of her 8 littermates. They do vary a bit in coat type/colour among her litter but their temperaments are pretty similar, which is the main thing.