I wouldn’t sweat a lot about accessories until your buy and ride for a bit, and I agree you won’t feel much difference in the 2014-2019. Now let me contradict myself my telling your about accessories that I LOVE.
Seat - I hated my 2014 stock seat and replaced it with an Ultimate seat. To me, the transition from the driver’s seat to passenger seat poked me in the back. However, I’m the only one I’ve read who listed that complaint, so take it with a grain of salt. Also, even with the Ultimate seat I used an AirHawk cushion. Some people love the Mustang, Corbin and Russell Day Long seats.
Grips - I hate the skinny little bicycle grips the Spyder’s come with. For less than $20 you can buy Grip Puppies that make the grips thick and squishy (in a good way).
Drink holders - I love a cup of coffee on most mornings so I bought a RAM drink holder that I mounted to me left handle bar with a Providence RAM mount, and another mount on my right handlebar with a RAM-X phone holder (I used it to watch my blood sugar levels).
Hopnel Bags - Big Bike Parts sells a set of 4 duffle bags by Hopnel designed to fit perfectly in the saddlebags, the bottom of the deep but narrow trunk, and another that sets on the top part of the trunk.
Lighting - I added lots of lighting to my 2014 because ... I just don’t know when good enough is good enough.
Again, no two people accessorize their’s the same way. Lots and lots of options.
Enjoy.