We don't use collars for our adult dogs, we don't like to pull their neck and their body languages is much easier for them with a harness.
We first thougt they would pull the leash even more but the training from Turid Rugaas helped them stop pulling even with a harness.
But, (in Holland) it's difficult to find a fitting harness because most will irritate the space between the front legs and the chest.
We have a special harness for them that has no piece between the legs.
For our puppie girl we don't have a harness, Basenji puppies have so much skin and a harness will irritate their skin.
We have a collar, just a normal collar, with a special soft fabrick for her neck. She likes it very much.
And our harnesses:
Our dogs only wear their harnes/ collar when the are outside.
We don't use them inside because there is no reason for us to hav ethem on with them..
And I would use a identification tag at the collar/harness with your phonenumber and the name on it.