There are no current legal Balance combos in Metal Fight Beyblade. I believe 100 is 0.5 mm shorter than 105; that would be the presumed difference. I can break up combos based on your parts, however.
Attack: Storm Pegasis 100RF (Good; used to be top-tier).
Defense: Rock Bull C145WB (Mediocre; use a MF and an Earth Metal Wheel to make it top-tier. Alternatively, GB145 and RS can be recommended).
Stamina: Flame Bull 145S (Mediocre; S has poor balance. Use SD instead, and Burn or Earth Mold 1 to make it a top-tier Stamina Beyblade).
Attack: Storm Pegasis 100RF (Good; used to be top-tier).
Defense: Rock Bull C145WB (Mediocre; use a MF and an Earth Metal Wheel to make it top-tier. Alternatively, GB145 and RS can be recommended).
Stamina: Flame Bull 145S (Mediocre; S has poor balance. Use SD instead, and Burn or Earth Mold 1 to make it a top-tier Stamina Beyblade).