A variable speed pump will nearly always be more cost effective over the life of the pump. Yes it costs more up front but it will save more on electrical costs even if you run it at higher speeds for part of the cycle (I do this on my two speed). In my signature below is a link to "Pump Modeling Tools" which contains a spreadsheet that I put together which will compare the lifetime costs of any pumps that are in the CEC database. But without doing the analysis, I can tell you that the VS pumps will usually come out ahead but it depends on what you pay for electricity and if you will also need a controller.

As for your questions:

#1 - Yes, you will need to run the pump at higher speed for solar if you have an elevated installation AND you have a vacuum release valve near the top of the panels. You can lower the VRV and make solar work at lower pressure and flow rates but then the efficiency of the panels will suffer. But still, a VS pump will allow you to tune the flow rate to be just enough to keep the VRV closed and the panel efficiency up.

#2 - Yes but so what? You are saving money. If you want to impress vistors, just up the RPM of the pump for the party.