I figured out even before I installed that there would be no way to optimize the heat exchange between panels and the water by guessing RPMs, or even by trial and error. The manufacturer of my panels clearly states how to optimize them, and they would know, and they spec that in flow, GPM (gallons per minute), not RPM. The RPMs are not really something to use for this, because of the many variables. Type of filter, height to roof, length and size of pipes, size and type of pump, etc. Every pool would be different. It's possible to guestimate flow by doing a lot of measuring of your plumbing and equipment, and then applying some math, but you only end up with an estimate. That wasn't for me, so I installed a flow meter that actually tells me what my flow rate is! EZPZ. No guessing, no measuring, no math. I just look at the flow meter and adjust the RPMs for the perfect amount of flow through my panels (which is 40 GPM).
The FlowVis I bought for this purpose was about $150. I figured that would be a one time expense, for a one time use, to dial in my panels, and just considered it part of the installation cost. But it turns out I use the flow meter for all kinds of other things, in addition to keeping an eye on the flow though my panels, which does change over time. So if I had to do it again, I'd want a flow meter even if I didn't have a solar system, it's that handy.
If you have a Jandy check valve in your system, you can buy just the guts of a FlowVis for about $100, and it'll retrofit right into your Jandy (you won't have to cut PVC or re-plumb anything.
So you can try the math. Or hold your hand in front of the return. Or do some trial an error. All perfectly fine ways of getting close. But if you want it perfect, and want to know that it's perfect, I recommend forgetting about RPM and get the right tool to determine GPM...
Amount of solar time? However long I need to run solar to get the pool to the temperature I want. No hard and fast rules, just whatever works for that particular time of year. Also quite easy to figure out: if it's warm enough, then turn off the solar. Repeat tomorrow.
Oh, if you still want to know, I run my solar at 2200 RPM.