It was a bit annoying that anytime I upload a video that default tags from my YouTube settings would already be in place, mostly because it’s impossible to easily rearrange YouTube tags. You can move your cursor to the front of the tags and type in a new one, but then your cursor automatically jumps back to the end.
If you need to rearrange a lot of tags on a YouTube video, “select all” and copy them all to a text editor. Then write your tags, separated by commas with no spaces between the end and beginning of a tag and it’s separating comma (i.e. tag 1,tag 2,tag 3). Then, in the text editor, select all, copy, and paste into your video’s tag field on YouTube. It’s a lot easier than trying to rearrange them inside of YouTube.