If you have more than one pressure tank...
You can have them close together. The supply pipe from the pump would have tees branching off to each tank. It is best to use flexible hose and if more than 2 pressure tanks are in tandem, then the main supply pipe should be larger than the branch pipes.
The tanks can be any size but the pressures must be the same. The pressure will regulate the filling rates.
You can also have two tanks a fair distance apart and even at a different elevation of several metres but the pump's supply pipe needs to connect to a common supply pipe at mid distance to equalise the supply path distance.
The tank's factory supply pressure can be altered by a big margin, see the previous linked PDF. A pressure tank's pressure fluctuations will be less if the tank has a higher pressure setting. The pressure switches used when pressure tanks are fitted generally come with 20/40, 30/50 and 40/60 psi cut in & cut out settings. Because it takes 4 times the head to double the flow rate through a same sized pipe, the higher pressure settings obviously have smaller pressure fluctuations.
A variable speed controller works great with a pressure tank but the tank's pressure must be set at 65% of the maximum system pressure. This means that the tank normally requires a pressure increase.
I found the controller I previously linked in another thread. A simple trick here...if you go to a persons profile and click on their post count, all of their posts will come up and a search box will also appear under the avatar. If you then enter a key search word, posts with that word will then come up. I went to my profile and entered "variable" and quickly found the correct post. The controller is linked below. There are others available but corporate_misfit has done the research and swears by this one.
http://www.dgflow.it/products/variable- ... phase-pump
When you buy a pump and if you are using a pressure tank, don't but the standard pressure switch.