I am going to compare the variator to a multiple gear type transmission.
Lighter weights means more rpm sooner (at lower speeds)
(like a on a gearbox type tranny .. if you left it in first gear longer before you shifted)
Heavier weights makes it act like you've changed to higher gears already.. even though you are not going very fast.
So a variator on a 50cc set up for racing (to give maximim acceleration) ... will have light weights in it .. since small motors have to be revved high to get maximim HP .. you have to set the variatore up to get high RPM sooner... so that you can take advantage of the greater HP at higher RPM.
This can make it a little annoying .. (for me at least) to have it on a bike just meant for street riding ... because sometimes you will be riding around not wanting to go fast and it will still be revving high all the time.
So .. you might have to try 2 or 3 different weight roller sets to find what YOU like.
It also depends on how the porting of the big bore kit is set up .. it may or may NOT be set up to make its best HP at high RPM .. (I don't have any experience with aftermarket big bore kits)