Benefits don't cap out, but I wouldn't go too extreme as mice are inconsistent at incredibly high DPI, and it can cause conversion issues for some games since many have ungenerous sensitivity sliders or suffer from negative acceleration if the sensitivity value is too low.
WPS is bypassed, that is the reason why you lower the game sensitivity instead.
If 1600 DPI is your preferred 2D sensitivity, then increase to 3200 DPI and set 4/11 WPS. In the calculator, raise the DPI to 3200, halve CSGO's sensitivity, and then convert to PUBG. I would usually recommend 3/11, but not in your case since 1600 is a pretty high baseline, and 6400 DPI is pretty extreme for the majority of cheap mice.