In Georgia, you can not tow a skier without an observer. So the answer is none.
an observer or a wide-angle rear view mirror on the PWC
It depends on the boating laws in the state you're in but typically you need a seat for the driver, spotter, and skier. Therefore the PWC would need to leagally be registerd to seat 3 persons.
an observer or a wide-angle rear view mirror on the PWC
You don't. The RX is not a three-person PWC, so you can't tow a skier. You need a driver, an observer (to watch the skier and tell the driver if they are in distress), and a skier. That's three people. By law, the skier counts as an occupant of the craft. By law, you must have an observer on the PWC so the driver can concentrate on driving.
an observer or a wide-angle rearview mirror
You are towing a skier with a PWC and have an observer on board. How many people must the PWC be rated to carry?
At least 3- an operator, an observer, and the skier
Three
1 hour after sunset and 1 hour after sunris
If you use a PWC to tow a skier or person on a tube, the PWC has to be equipped with mirrors or you will need a spotter over the age of 12. The person being towed counts towards the capacity of the PWC. (If you have a spotter and are pulling one person, you would need a PWC rated for three (3) people.)
No. The GP1300R is a two-person PWC and you need three people to ski: A driver, an observer (to alert the driver if the skier is in distress), and a skier. All count as occupants of the craft.