Here is a video from Max Tech channel. While he tested 4K footage, and I said 16GB is preferred for 4K footage, they still tested it on 8GB. It can still be done, just slower. So if you are on a budget, it can still do 4K at 8GB of RAM. I wish he would have tested 1080p. 4K is too common these days where 1080p tests are not really performed.
Go to 7 minutes in.
1080p is so lightweight these days where 8GB of RAM is no sweat for it. Comparing 8GB of RAM on my 1080p footage and 128GB of RAM is only a few seconds difference. Not really worth it. 1080p is very low standard these days.