Yes, the Pacific grommets should be a direct fit to the older Fischers.
Those Fischers are really unique. The Pacific frames have a different layup; it should be expected that their feel would be different too. And yes, Fischer's recommended tension range is very narrow on the midsize Vacuum Pro.
I've played both Head PC600 and Vacuum Pro 90; to me, the Fischer has better ball feel, is more innately powerful, feels a bit "livelier," and can more easily impart spin (by virtue of its less dense pattern). I like the Fischer better, and still keep a few of them around to use. The only downside of the Fischer Vacuum Pro (90 or 98 ) that I can think of is that the grommet doesn't really serve as a decent bumper guard; these frames show court rash terribly and begin to chip and wear into graphite shockingly quickly; extra head protection tape is advised.
Have fun with them!