I assume that youv'e noticed some transformers get a re-deco as some different transformers or as an "upgrade" in the same line (Armada, Energon, Beast Wars etc,) well, a while ago, I searched the 'net for various versions of the Armada Optimus Primes, Overloads, and Jetfires.
Here are my findings:- (not too up-to-date, as I haven't checked recently.)
Jetfire. (Space shuttle/robot/alternate legs for combined Optimus form, sometimes refered to as "Rocket pants", as opposed to "trailer pants" for Prime's truck trailer's third form.)
4, armada (normal version) powerlinx, (dark blue legs) armada k-mart, (darker grey legs than Armada) and micron (dark grey legs, no yellow on the "lapels").
Overload. (Jet\shuttle carrier/robot/heavy weapons emplacement for super Prime's base/shoulder-mounted cannons.)
7, Armada, Energon Ultra Magnus (Blue and white), Sentinel Maximus, (exclusive to OTFCC 2004) (blue with gold torso, red with gold upper arms, blue and white lower arms, white with black upper legs, blue with gold lower legs, mouth/nose like Optimus' face-shield), Costco (yellow with dark red and some white decals), Micron Densetsu Clear Ultra Magnus (dark red, semi-transparent,) (Japan/china only, I think,), Micron Densetsu (non-clear) Ultra Magnus, (Similar to the clear version, but (unsprisingly) not semi-transparent), Teal Ultra Magnus (No information yet.)
Optimus Prime. (Trailer-truck/robot-automatic transform base/Super robot-"trailerpants".)
7, armada, K-Mart (gold coloured cab, shoulder decals and "ear-fins"), costco (similar colouration to Costco Overload), Final battle (Dark blue and dark red colours, blue-grey arms), powerlinx (not sure), micron densetsu, (like Armada, but the yellow is more "there"/prominant) micron densetsu DX (similar to Final Battle Optimus Prime, but with black along the sides of his "trailerpants".)
Now, minicons notwithstanding, you can swap the torso of Super Prime with the legs of either Jetfire or Primes' own legs, and with the various redos of Overload, giving a sizeable number of possibilities.
028 Optimus' with Jetfire's legs,
049 Optimus' with his own legs,
196 Optimus' with Jetfire's legs and Overload's in shoulder cannon mode,
343 Optimus' with his own legs and Overloads' in shoulder cannon mode
Which, if you add it all up and hop the Transformers dimensions, comes to (if Iv'e done my maths right,):-
626 different Armada-universe Optimus'!
Quite the army!
Brock PHillips.