Electrode 1 and electrode 2 must be bonded together, so the question of which to connect where is somewhat academic.
Basically true. However there are some situations where two or more GEC's are bonded to the grounded service conductors at different points at or prior to the MBJ.
In any case however, an EGC (which is always a load-side grounding conductor) must always bonded to the MBJ/SBJ on the side opposite the grounded conductor (assuming it is a grounded system, of course*).
*In the case of an ungrounded system, everything is the same except there is no MBJ/SBJ.
The only electrodes not unconditiomally required to be bonded together into one GES are lightning protection electrodes and auxiliary electrodes. Yours are neither.
Auxiliary electrodes are bonded to the GES through its "GEC" and the circuit EGC. Additionally, Code has no provision(s) that I'm aware of to not bond lightning protection electrodes from the GES that qualify as Code "defined" grounding electrodes at the structure.