Gallium nitride (GaN) lets a charger run cooler and smaller than the silicon bricks we all carried ten years ago. The trade-off you are actually shopping for is wattage, not size.
65W covers a 13-inch laptop, a phone and earbuds at the same time — the sweet spot for a daily carry bag. 100W is for 14/16-inch laptops or anyone who wants to top up a power bank as fast as a wall outlet.
Whatever you pick, look for two things: USB-C Power Delivery on every port, and a foldable plug if the charger is going to live in a bag. Everything else is marketing.