Hello,put on the CPL filter or mist filter then screw on the Variable ND on top.Stacking filters in general can create different effects and bring out your creativity. The only caution is that as you put more filters on the lens you can create vignetting or the cutting off of the corners of your picture. This can happen more with wide angle lenses. You’ll also get vignetting by stacking neutral density filters, depending upon which ones you stack and the order you stack them you’ll get varied effects. We don’t recommend stacking a VND filter but if you do, make it the last one because of the threads. 

Not for water activities like swimming, it 

Yes it does...I have a Spigen case on my iPhone 13 Pro Max and fits no problem at all and that clearly is bigger than a standard 13 Pro. Regarding the Gimbal, it's a great bit of kit and works brilliantly!! 

Must take where the "connection width" is 19mm. 

Yes, the heart rate and blood oxygen sensor record continuously around the clock, and give timely warning when the resting heart rate is too high or too low.