In my years of driving Volkswagens of all vintages I have never encountered any issues but I too have read about the issues and the available remedial accessories. I have driven a bug in excess of 120 km / hr for long distances and that included lane changes and cornering..ok maybe not cornering at 120 km but without reducing speed significantly. I think more of it comes from 'knowing' your bug , having confidence in its abilities and identifying its limitations. There are things your 50 ish years old bug can do and there are things it can't. The things it cannot do, I suggest you don't even try regardless of the modifications you can throw in....just buy a sporty piece of engineering
I have heard of the modifications / accessories that you mention but do not have a first hand experience of the improvement in performance, if any, they bring. I have not seen any being sold at the shows either (or maybe I wasn't looking in the right places)