centrifugal

I don't know your level of knowledge.

Assuming that it is minimal I would suggest some reverse engineering because most of the answers will be available to you.

Take any high pressure pump in the range, from the pump curve select the duty point at the highest efficiency. now inspect the volute and impeller.

then take a low pressure pump and do the same. the inspection will reveal some differences. Ty and figure it out. Why - why-not.

Then go and ask the engineer why the difference. By then you would have learned some design principles.

If you then like it continue doing that. You will at least catch the attention of somebody.