For me "cheese" means anti-immersive implementations, oftentimes unbalanced and more often than not needlessly and crudely injected into the game despite there being a plethora of objectively better D&D alternatives, because Larian loves silly fun that much - and moar iz betta!
Pickpocketing is an example of cheese that likely won't change, DOS2 had the exact same issue. It is essentially a never ending dispenser of free stuff. Once you know the mechanics/savescum, there is zero risk for almost no effort for the best supply of loot and gold in the game. Totally breaks any sort of reward vs. risk balancing mechanic. You might say you can ignore stuff if you don't like it, but you still feel punished for roleplaying (anything other than an amoral kleptomaniac) in the game. This is pretty bad for a roleplaying game that takes itself seriously and that attempts to walk in the shoes of the BG classic (who at least had a balanced law & order system). And this is but one of way too many cheesy half-assed implementations.
Your example to counter the use of barrel is a good one. You could also make those barrel heavier - the player might not be able to carry too many of them. There might be other options.
My ideal game would reduce encumbrance capacity drastically. Realistically your entire party shouldn't be able to carry a single barrel - without reducing movement speed to a crawl. So the cheese is in several layers. This isn't based on "muh realism" as it might sound, but a certain consistent internal logic is helpful for immersion. The loot focus (that detracts from the character build focus), most of it trash or unbalanced homebrew, feeds into this. Larian's insistence on excessive loot is why I never finished DOS2, and I imagine partly why the large majority of players never did.