You have asked a loaded question, because everyone has their own opinion about what is best, and why.
You have copper piping, which pretty much lasts forever in most homes, unless you have acidic water. PEX is becoming more common primarily because it is faster (cheaper) to install, and raw copper prices are through the roof. CPVC is not widely used for new construction or re-piping here in the Midwest, but I have used it for smaller jobs with no issues. It is also inexpensive and easier to install than copper. One thing to remember when installing PEX or CPVC is that the I.D. is smaller than the equivalent copper pipe, so it is often suggested to install one pipe size larger than what is commonly recommended with copper.
The pressure tank you have now is fine as long as the bladder is good and you maintain the air charge. Do you need the room you will save by replacing it with a smaller tank? If so you might consider a CSV instead of the controller for the variable speed pump. The electronic well pump controllers have a pretty high failure rate, so I wouldn't suggest switching over.
If you have natural gas available, you should research the cost difference in heating water with gas vs. electric. In most (but not all) of the U.S., gas is less expensive. Depending on your water, an electric tank might last over 20 years. There is no guarantee that a new tank will last any longer than the one you have. The main thing to consider is what might be damaged in your home if your current tank starts to leak? A pan with a drain line can be cost effective if the tank is in or above a living space.
If the iron content of your water is relatively little, a softener alone will take care of it. What is more adequate for treatment would depend on the results of a complete water chemistry analysis.
If I were you, I might look at what will minimize the chances of an expensive plumbing failure, like heavily corroded piping or old washing machine hoses (likely to burst). If your existing plumbing is in decent condition, you might be better served by putting in some updated fixtures like shower valves with anti-scald technology or looking harder at your heat/cooling losses and weatherization.