I, like many on this forum, used to stand while performing. I thought it made me look more like a was playing the keyboard and that people could see me better. That was a fallacy.
For the last 15 years I was on stage, I used a great stool that has a backrest, footrest, a heavily padded seat and fully adjustable. It weighed just over 25 pounds, and folded flat for easy transportation. I found that it immediately made me more relaxed while performing, it really had no effect on my singing and at the end of a performance, I no longer had an aching back from standing for one to four hours.
As for audience visibility, the stool positioned me high enough that the audiences could see nearly as much of me as when I was standing. So sitting as a no brainer for me. And, when I performed 3 to 4 hour jobs, sitting made it so comfortable that I rarely took a break during the entire performance, and if I did the break was just long enough to go the restroom and return.
Good luck on whatever you decide upon,
Gary