The simple fact is, these are the most power hungry cards in the market, and they put 2 or 3 connectors for a reason. 340w is required to ensure no issues, i don't believe splitting one cable power into 2 is wise move. My old 1080ti used 2 8 pins and used 250w, my thermaltake 750w thoughpower was definitely pushed to get that power out, i doubt
Power requirements will vary from system to system depending on the hardware you have, however daisy chaining is not a good practice, and to even suggest this is ok on a 3080 is nothing but ridiculous. If you have a good power supply you should be able to get 3 8 pin and avoid daisy chain all together. Just because it works, doesn't mean it works as it should or efficiently. I recently upgraded to a 10gen intel, and my old 750w thermaltake thoughpower had to be replaced, due to 2 8pin, if daisy chaining was ok i wouldnt have bothered but clearly you havent built enough systems to know what you are on about, also each rail will have a maximum output so daisy chaining is limited to the max of that rail.