Girdles are only needed on GSR and ITR motors, or on LS/VTEC motors (these need girdles because of the even longer rods in the B18A/B) because of the rod/stroke ratio. The rods are longer, hence more material, and they have a larger moment of inertia... This is why B16 blocks do not have them, nor do they need them.

As for heads, GSR has less volume, hence will gove more compression. The B16 heads "flow better" because of the intake ports. On the GSR they are slightly different to accommodate the variable length intake manifold.

Work on any head is only good for top-end power, who cares if u can get an extra 10 hp on top end (7600-8000) if you lose power lower in the RPM band.

And as for the pistons limiting the redline, this is incorrect. Pistons simply transfer the power to the rods, the rods are what rotate, hence they have a larger moment of inertia, aka once moving they are harder to stop, remember physics class??

As for tuning with a vafc, good luck... someone already said that it has no spark control, and I totoally agree. For the same price as a VAFC ($200+) you could get an eeprom programmer and use uberdata or the like.

As for B18hatch, I would go with whatever is cheaper, however, the differences are slight, and if your going all motor a GSR will yield a higher C/R.
In addition, GSR heads are said to have better cams, although this is also not reeally important unless you are really going to build the motor for all-motor use.

But I would say one additional thing, the VTEC motors are ENGINEERED to rev-high and the non-vtec motors are not, so take care in revving them too high, or you might end up with a rod shooting out of your block .