The vernier adjuster makes it easier to adjust but I can't see how it would affect handling. Possibly the old rubbers were trashed and needed replacing. The Dave Taylor head steady improved the handling greatly on my '72. I used one for quite a while and now using the CNW one. Made a huge difference in my bike.
I'm still using the shimmed isolastics and it really is no problem. You don't have to set these very often. Someone recently mentioned on here that they preferred the factory verniers which require modification of the older iso mount in the front (cutting 1/4" off squarely), over the aftermarket kind that do not require any mod to the iso mount (Hemmings?). Is it because there is more room to work with? Years ago I bought an extra front iso mount to modify but never got any further.
'72 Combat Roadster 2020xx
'61 Matchless G3 350, ex-Dutch Army
'09 H-D XR1200