Would an overclocked 5600xt be better than a normal 5700 then?
It somewhat depends - the issue with the 5600xt is the fact it uses only 6gb of GDDR6 memory on a reduced 192 bit memory bus compared to the 5700 running a full 8gb on the full 256 bit bus.
Different games require different things out of the gpu - some games scale best with core clock speed (e.g. Forza Horizon 4)... in those titles the reduced memory size / bus width won't matter much so you might be able to outpace a 5700 at stock speed. However other games are more dependent on memory and then the 5700 will always win due to having the stronger memory system (e.g. the new Doom Eternal won't even allow you to enable to highest graphics settings on the 5600xt as it doesn't have enough vram).
So effectively the 5700 is going to be more consistent - I also think 8gb of vram is the sweet spot moving forward. 6gb cards are enough for most games right now, 4gb cards are really the minimum you can get away with. In another year I think 6gb cards are going to struggle in more games.