Digiarty's multi-lingual WinX claims to allow downloads from 300+ sites—including adult sites. Perhaps the biggest selling point of all is the claim that "There is no malware, adware, spyware or virus. 100% clean." The latest version has a much improved interface as well. There are ads, though—on install, I was asked to upgrade to its $29.90 product for Windows and macOS called VideoProc, which does everything that WinX does, but for 1,000+ sites, plus offers some editing for high-end 4K/UHD video.
This program is straightforward to use because there are only a few simple steps to download YouTube videos and channels. The first is that you need to copy and paste the specific URL for the video or channel that you’re trying to download. From there, you get to select the specific video resolution that you want to use. Then, just download the video. It really is that simple to get the access you’re looking for. If you want to convert the videos that’s an option too, so you may want to check it out as a free option.
The Chrome Web Store—where you get Chrome browser extensions—is controlled by YouTube's owner Alphabet/Google. Even an extension ostensibly for this purpose—like the obviously named Video Downloader professional above—states right up front in its description, "The download of YouTube videos to hard drive is locked because of restrictions of the Chrome Store." In general with Chrome extensions, the download of any RTMP protocol video (protected videos) or streaming video isn't possible.
The cheapest of these plans is $8.33 /month for 1 TB of backup space and support for 10 devices (and three sub accounts), if you pay for a whole year at once. You can add more for the same price and storage, like another 1 TB for another $10 /month. The maximum storage plan you can pay for is 15 TB, but if you want more you can contact their support team.
NOTE: Beware of the ad traps on some helper sites—ads that look like they should be the download button to get your desired content, but they are not. Also, depending on the ad network employed by the site, your own virus detection software may throw up some warnings. The more the developers of sites rely on ads they don't control, or resort to trying to get you to place something on your system as "payment," the worse off we all are.