A 200cc or 250cc standard motorcycle has enough power for 55 mph speed limit roads, and a 250cc Kawasaki Ninja or a 400cc Suzuki Supermoto is enough for 70 mph roads, but they will not have a lot of comfort at this speed, and they will get blown around some by big trucks going by. With these you will be ahead of most cars for the first quarter mile, but almost all cars have a higher top speed. (The vehicle with the lowest top speed for the last 20 years is a diesel Hummer- 80 mph).
An 1,800cc Honda Goldwing is the most comfortable for a long trip, and a 50cc scooter is the most fun at 30 mph. For what is most stylish, opinions vary greatly. Some prefer a less comfortable racing style, some an antique Royal Enfield or Harley style, and some the easier no shifting scooter with floorboards that keep your clothes cleaner.