Most of the time the performance difference between two GPUs of the same model is within 3% of each other (a 3080 with a 3080,, a 2080 super with a 2080 super, etc). In real life it should not be noticeable.
The difference between differenct brands or models from the same brand, are cooling solutions, power delivery, aesthetics and some factory OC. Some may also have hand picked silicon for better overclock but those are also labeled as such and are usually more expensive.