I'm in a similar boat picking between the Nikola and 16x. I got a really beat up Tesla for very cheap and I've since ridden 700 miles (wheel total is 2200). I've been wanting to upgrade for QoL improvements as I mostly use my Tesla for my commute. It doesn't have a lift sensor, the peddles are small and can get uncomfortable on longer rides (my commute is 7.8 miles). Speed wise I usually peak at 28ish and have an average riding speed of 18mph according to darknessbot. I also currently go to college and need to take my wheel into buildings and classrooms and into my apartment complex where I need to open my front door, go up a short set of stairs, then open another door, then go to my apartment so having a lift sensor that I can effectively use with 1 hand is rather important.
I have had the opportunity to ride both a little bit (no extended tests yet), just around a parking lot/streets and I prefer the way the 16x feels. Personally the Nikola feels really bulky and boat-like to me, while the 16x feels closer to my maneuverable Tesla. However, in comparison there seem to be a lot of issues with the 16x that are making me hesitant. I do bring my Tesla up to 30 at times so it starts beep and I'm comfortable at 30 but I don't think going above that is a needed requirement for me. I just don't want to be thrown off and fall.
I'm also 5'11" and 165-170lbs if that makes a difference