Sharing big video files privately can definitely be a hassle. A private YouTube channel is a solid way to go - easy to link without size limits while keeping it locked down. Google Drive is another good option for sharing large links that expire. For client privacy, Hightail Spaces is more secure but overkill if it's just diagnostics.
Lots of ways but I just throw it in my gmail. It will send it as a shared folder and you will have to grant permission (a popup after email is sent) anything under 25mb sends, and anything over goes as a shared folder.