I did a bunch of research on breakaway collars, etc., and finally decided to just get a lightweight regular collar for my grey's tags and leave it really loose. It's all about your comfort level, but I feel okay about it. (Like you, I did NOT feel okay about leaving a martingale on him all the time, even though the adoption group said it was fine.) In all but really unusual circumstances, he could back out of his tag collar very easily. (Our dude is also VERY lazy and rarely leaves the couch when we're not home, so if you have a dog that is wilder inside, maybe it's a different equation.)

It's this one in 14.5-20", and we leave it so that it sits loosely on the biggest part at the bottom of his neck: https://www.amazon.com/gp/product/B017CPPSZM

Another part of my decision for our particular circumstances: the risk of him getting hung up on a non-breakaway collar is not zero, but we live in a small house in an urban area, so the risk of him bolting out of our front door into a dangerous traffic situation is also not zero. This is a compromise: not a martingale that tightens, but not a breakaway that doesn't let me hold onto him briefly just to make sure he doesn't bolt out of a door.