Passenger comfort was a priority for us when we changed from two bikes to one.
We experimented with various size pads before getting a local upholstery shop to make up the one on the top box. My wife has back issues and she couldn’t ride for more than an hour at a time without this and it was a cheap mod.
The Sargent seat is immeasurably more comfortable than stock (and possibly a bit higher).
The Ilium floorboards were crazy expensive to buy up here in Canada but they seem to have made a huge difference. They’re 3/4 of an inch lower than stock and the only difference they make to me as a rider is that I have to remember to fold the lhs one when using the centre stand or else it gets in the way. My wife says the boards allow her to brace better for braking and move her feet around more for balance and comfort. She LOVES them.
(Forgot to add that she’s 5’6”)