New Pug Puppy

I should be getting a pug puppy soon, and I just have a few questions regarding collars/harnesses
1. I want to get a harness, but what size do you typically get for a puppy (8 weeks). Is it better to get a harness for an adult size and adjust it as the puppy grows.
2. I'm worried about getting a collar because I've heard it can be risky for pugs, but I want to put his Id tags on it. Would you recommend getting a collar (and again should I get a size for the adult pug and just adjust it for the puppy) because I would attach the leash to the harness, the collar would just be to have the Id tags?
Thanks so much!!