Why change the muffler unless you want noise? Just because a muffler is loud doesn’t mean your bike is going faster, it’s just loud. Stock mufflers are precisely engineered for back pressure, torque, useable powerband and overall performance. An aftermarket muffler will sacrifice one thing or another.
Not really sure that the Honda belt drive ADV is built for racing. Though if you’re looking for something with more flexibility ADV type, then consider getting a BMW G310GS, Honda 500x or Kawasaki Versys, all good bikes, unless of course you’re only interested in automatic.
Consider spending a week or two renting various bikes and make your best personal preference decision based on your personal experience is probably your best personal advice.