Also. What is the benefit of using a booster pump to pump out of a tank over a submersible well pump dropped in the tank? I read that booster pumps can't increase volume and only increase pressure. I feel like a half horse well pump could do everything my 1hp booster can do.

Thanks!

Any chance you could elevate your tank high enough to get enough pressure both gardens? Then your 1 hp pump could simply fill the tank when needed using a simple floaty system. Might be able avoid a second pump that way.

To answer your questions I believe will require some math regarding flow rates, pipe lengths, pipe diameters, etc. which is beyond my capabilities.

If you purchased a variable speed booster you could dial in the desired boost. Variable volume/pressure. Unfortunately they are a bit more money than the on/off types but they consume less energy with the power draw going down by the cubed of the speed. This allows you to control the amount of water/ thus the power you use.
Look over this product . Perfect Pressure Pump . I believe it will fix your issues.
All the best,
Phil