An analysis of two-pump optical parametric amplifiers is proposed in order to evidence strategies to project and develop flat two-pump fiber parametric amplifiers (2P-OPAs). Amplifier gain profile is evaluated through a model that takes into account the four-wave mixing process with pump depletion. Disturbing influence of degenerate three-wave mixing processes is separately addressed. Through the analysis, important 2P-OPA project guidelines are obtained. Theoretical forecasts are confirmed by experimental measurements on different 2P-OPAs, realized by changing power and spectral allocations of the two pumps, obtained by Raman amplification.