BackBlaze doesn't have an offline component, so you'll have to handle that yourself, but it's by far one of the most affordable options on the market. Accounts are $5/mo (you get a break if you pay up front for one or two years), and you can add more computers to the same account for another $5/mo. You can read more about Backblaze's pricing options here.
To protect your channel from COPPA, you can download all videos in the channel to your computer for backup or re-upload them to other platforms. Since online websites do not support batch downloading of videos, and most of them have suspicious and unsafe ads embedded, thus, it is better to use a safe and reliable tool like Jihosoft 4K Video Downloader.
There are a few common practices for configuring when backups occur. The most common option is on a fixed schedule, such as once a day, week, or month. The second, which we prefer, is to upload file changes whenever they're changed and saved, otherwise known as a continuous backup setting. Services only transfer the modified part of the file in this scenario, so as not to overburden your internet connection or take up unnecessary storage. A third way is simply to upload files manually. Some may appreciate this degree of control, but this method is only effective if you remember to regularly run the backup.
If you deal with videos professionally and need to be in constant collaboration with clients and colleagues, Google Drive can’t be beaten to backup videos. Its integrated file sharing option is a breeze to use, and all you or anyone you share your files with requires is a Gmail account (and let’s be honest here, who doesn’t have a Gmail account these days?).