The Sony a6400 may just be the best YouTube studio camera setup right now in my opinion. It offers so much value at this price point and this is a camera that you can grow into for many years to come.
I've reviewed this camera a number of times on this platform and I've used it both professionally outside of YouTube, and of course for my YouTube videos.
I think one of the reasons why this camera is so popular really comes down to the number of features you do get for the price. This is a great low to mid tier starting point when it comes both the new and experienced filmmaker.