I have a 500cc scooter and have ridden with guys who have the Burgman 400. That is a great scooter and would make a great first bike. I’ve found that the larger class scooters (400cc and above) don’t fit into a nice classification. They are not part of the scooter sub-culture and they are not really bikes but they are no more different than a cruiser is from a sport bike. But none of that matters if all you want to do is ride.
I ride with a group that is mostly cruiser riders and some of them have admitted to me they had a scooter prejudice before they started riding with me. Now they know they cannot keep up with me in the twisties and want me to lead rides.
As you ride you will learn what type of riding appeals to you and you will slowly find a group who have similar tastes. Honestly that is much more important that what type of bike you have, so if a 400cc scooter appeals to you I say go for it.