I decided to give this new feature a try and wanted to share my opinion. You can find it under Settings -> Gameplay -> General -> Customization. The OFF setting hides all flags, decals, paints, camos and majority of skins on you and other players on all regular vehicles and number of premium ones. It seems to be especially great to avoid seeing displaying (upcoming at day of wring) skins such Archangel or Kraken.
Existing issue is with the myriad of re-skinned premium vehicles oe/mail ru created in past
Some vehicles despite they have sibling "skinless" model, such skin-only have "customization" disabled for their owners (based on wide variety of reasoning of game owners). The "Customization" setting copies this rule to other users (wanting to hide it), making skins such as Wolfs, Sharks, Black Eagles always visible.
Some vehicles don't have bare skin-less models - they don't exists for many reasons - examples are Abrams MA1A1 AIM, T-14-152, Type 99A2-140, M60-2000, Vickers Mk 7/2. They are always visible with their "art". By the way, if customization doesn't apply, it doesn't hide flag too (that 10K gold flag).
I suggest that users of Customization OFF option should able to hide all (re-)skins with their bare color model. If AI models can have different camos on such vehicle like T14-152 and customization OFF hides it, the game should able to do same on players T14-152 skins (so and another vehicles as well).