If Ethereum POW stops today AMD GPUs like RX5600 and RX5700 will feel the heat of obsolete more than Nvidia cards because Nvidia seem to support more algorithms and still remain a bit Profitable than AMD if not mining Ethereum, for example Octopus algorithm is Profitable on Nvidia cards, the only option left for AMD cards will be Ravencoin and RandomX but they are less Profitable, am I right or wrong?
You are wrong because the main cost of mining is paying electricity bills.
Miners have very different prices for a kilowatt of electricity (from 2 to 14 cents).
Problems will start for those miners who have very expensive electricity.
Miners with cheap electricity prices will have a better chance of surviving, but the ebay will be overwhelmed with offers of GPU sales.