In this work, we present a detailed experimental study of pulse formation mechanism in an EDFL, hybridly mode-locked by use of a CVD monolayer graphene onto a D-shaped optical fiber and nonlinear polarization rotation (NPR), under a large intracavity dispersion influence (up to 100 times) ranging from 12.3 to 1382 m cavity lengths. Analyzing the spectral evolution, temporal and soliton behaviors of the pulse, our results revealed the presence of four laser operating regimes with non-soliton and soliton formation from short to ultralong cavity lengths, all related to graphene/NPR nonlinearities, dispersion and soliton propagation influences.