It used to matter, yt itself advised you to put your most important tags first.
However these days I think tags matter much less than they used to, and the order doesn't seem to matter at all. How it works now from what I've read is that all that it matters is that a tag is indexed in the meta data. Whether a particular tag is in the tags, the description, the title, the filename or the captions doesn't matter. If a tag is index'd it is index'd now.
What makes tags favoured over others in terms of SEO is no longer the ordering of the tags what makes a massive impact these days is watch time. Watch time is king. How a tag is ranked is if I upload a video and in my tags or in my description I mention funny cat. That video is indexed for the search term funny cat. It will show as a search result when I search for funny cat and will show as related to other videos that are index'd for funny cat. However the difference comes in when people click on my video for funny cat if they watch it to completion for lets say 4 mins while the watch time for all other funny cat videos is only 3 mins. Youtube's algorithm sees that when people are searching for funny cat they watch your entire video.
Saturating your target keyword in all your metadata probably still has an impact but no where near as much as it used to.
So lets say I take this video and now upload it, with the file name seriousdolphin.mp4, with the title serious dolphin, I mention serious dolphins in the video, put it in the captions, write the phrase in the description and put it in my tags. Youtube will see that my video is about serious dolphins so when I upload it is initially ranked highly in the search results for serious dolphins. However people will click on to the video then click off once they realise that there is no dolphin and it isn't serious. It's a funny cat. The watch time will drop and youtube will then know to rank my video waaaaaay at the bottom of the search results.
TL;DR: Order of tags no longer matters, that was soooo 2009