Like mouse gestures a proper picture-in-picture mode is really missing in Brave. In Yandex you just leave the tab with a running video (e.g. youtube) and the picture-in-picture mode starts automatically. Resize works fine.
In Brave I don’t even see any option to get into picture-in-picture mode. There are lots of useless extension duplicates in Chrome Store, which offer a not-handy button in the bar above or a semi-working button within the video. If started, resize doesn’t work properly and the video jumps out of the screen. As a modern browser Brave should be able to handle this. Despite of these 2 things Brave is great. But these are crucial things for me and it seems for many others.