Booster Pump

Here is my situation :

It looks like we are in the dry spot of the already dry Issan.

I have one 7 meter deep hand dug well ,which after a days rest will have 2 meter of water at the bottom . The deep well was drilled to 25 meters ,pipe is in to about 18 meters .

With good planning we can make it last for the house and the flowers ,but it is stretching it .

So I have a combination of the old type rain collection tanks ,some concrete rings ,even my hot tub -all plumbed together (a total of aprrox 15 cubic meters) with a 1.5 inch pipe at the end .

Here I want to install a Booster pump and plumb that into the house supply system ( fed by the 2 pumps -as mentioned earlier) I got the broshures for the Mitzubishi and Hitachi brands ,but it is all in Thai . Some things I can of course figure out . I do not want to oversize this ,since I am afraid to blow the PVC pipes in the house . An adjustable pressure pump would be nice . Then they are talking about an inverter ????pump -at almost double the price . Was is the difference ?

All I want is to pump water from the ground level tanks to aid /supplement the house water system . There needs to be a pressure shut off switch which will maintain the line pressure ,same as with the regular pumps .

Please you plumbing experts help me out.