5700 XT is a very high end GPU, especially the 16GB option (can you even buy a 5700 XT with16GB for PC? I can't find any in the local price aggregator, all of them are 8GB). It isn't the fastest GPU you can buy, but it is still a high end one.

If anything, this is the first time i see an iMac which has a good GPU. Though considering iMac's form factor and my experience of having a PC with a 5700XT i wonder about thermals.