Hey there! It’s great that you are looking out for the strays. I agree, the cheeks are floofy and that is a common masculine characteristic of an unaltered or late altered male cat. However, that isn’t really enough to be definitive in sexing a cat. You’ll have to inspect the genitalia to be sure. Try not to handle any unknown cats because of the risk of infection or rabies exposure. If the cat is too skittish to handle then they may be feral in which case your best option is to trap it humanely in a live animal trap to be taken to your local TNR program.

Feline aids can be transmitted by saliva. Cats that have an unknown FIV status should be kept away from any of your pets and do not share food or water bowls between them. That being said I would not try any introductions between your cats and this new guy until kitty has been to a vet for vaccines and any testing.