Stray cats or not?

I'd say not really...
lots of people don't put collars on their cats, either because the cat hates it or because they worry that the cat will get stuck somewhere and hang itself...

Healthy cats will keep themselves clean so a healthy stray that's getting plenty of food from people will probably be clean and neat.
a feral cat might be more ragged than this and might avoid people ... so if it's a friendly clean cat it's either some ones cat out for some extra food, or a stray that used to be some ones cat and is probably fixed and so not a really problem as it will not fill the area with hundreds of feral babies...
Stray cats only become a problem if they're not fixed and then you get feral cat colonies forming and that can be upsetting...

Take a Photo of the cat in question, and post it.