It seems that the II board used old school electrolytics that weren't surface mount, the IIx, the aluminum SMT electrolytics, then the IIfx could use either. The II also had soldered ROM chips with a ROM SIMM header underneath, whereas the IIx/IIfx had ROM SIMMs. Then, battery-wise, II's had them soldered, as did early IIx machines. Later IIx and the IIfx used battery holders.

-J