Thinner gloves or more grippy gloves are more effective as thinner diameter grips, although a thinner diameter does help.
Like velocicraptor I do think that 3mm is really thick.
I have Ripcurl heatbombs in 1.5 and 3mm, the 1.5 are heaps better in grip and not that much colder (bought the 3mm by misstake)
When it is really cold:
oceaniasport.shop/products/oceania-gloves-orca?variant=47233150615896They are ugly as hell, and a bit fragile, but with the under gloves you suddenly have really warm hands instead of that the cold is managable.
With the under gloves on I found them really really grippy. Without them they are a bit too wide for me.