3-wheel or 4-wheel — which is better?
Neither is universally "better" — it depends on where you'll ride. 3-wheel scooters have a tighter turning radius, which helps indoors and in tight store aisles. 4-wheel scooters are more stable outdoors on grass, gravel, or uneven pavement. If you'll do both, a mid-size 4-wheel model is usually the more versatile choice.
How do I know what weight capacity I need?
Add the rider's weight plus anything they'll routinely carry (a bag, groceries, oxygen tank). Don't buy right at the limit — a scooter rated close to its max capacity will feel less stable and the battery will drain faster. If you're between two sizes, size up.
Can I take a scooter on a plane or in a car?
Portable/travel scooters are designed to disassemble into 3-5 pieces, each light enough for one person to lift into a trunk — that's the category to look at for travel. Full-size scooters generally need a ramp or lift to load and aren't practical to check as airline luggage without advance arrangements with the airline.