Abstract Background Compared to conventional dose rate irradiation, ultra‐high dose rate irradiation provides superior normal tissue sparing. Multi‐energy proton beams combined with a universal range shifter (URS) and fast energy‐switching gantry enable ultra‐high dose rate delivery. Purpose This study investigates the effects of the URS, planning parameters, and patient selection on multi‐energy Bragg peak (MEBP) proton FLASH radiotherapy (FLASH‐RT) plans. Methods Single‐field plans were generated for water phantoms and a brain case, comparing beam setups with and without the URS. Planning parameters, including spot spacing, layer spacing, and beam orientation, were varied. The effects of fractional dose and target size were also assessed. Dose and FLASH‐related metrics were analyzed. Results The use of a URS increased the spot size, which reduced the number of required spots and energy layers but also resulted in a broader penumbra, a prolonged distal falloff, and a higher D mean in normal tissue. These effects became more pronounced with greater URS thickness. A spot spacing of 1.5 times the spot size (σ) and a layer spacing of 1.0 times the Bragg peak width (Proximal and Distal R80) improved V 40Gy/s , while effectively maintaining plan quality. Beam orientations with smaller field sizes increased V 40Gy/s . As the fractional dose increased, V 40Gy/s also increased, reaching saturation around 25 GyRBE. Additionally, V 40Gy/s improved with smaller target volumes. Conclusions The URS has a significant impact on plan quality, requiring a balance between normal tissue sparing and the FLASH effect in MEBP planning. Although MEBP plan is suitable for treating tumors with complex shapes, careful selection of planning parameters is critical for achieving effective FLASH treatment.