Depending on how you are promoting your stuff on Youtube, you may be better off doing a straight redirect.
If you are getting a lot of typeins from Youtube (i.e. you are getting traffic from having your url on the video, as a pre- or post- roll ad or a watermark) then you need the shortest, easiest and most typable domain you can get. Therefore subdomain.maindomain.info is not a good option because people will either not be bothered typing that in, or they will screw it up and make a typo. Also a .com domain is much better for getting typein traffic - even if they read your domain on the video watermark as yourinfodomain.com, a good chunk of people will automatically type yourinfodomain.com into their address bar just out of habit.
If you are getting traffic from Youtube by getting clicks on the url in the description box, then obviously you can use whatever domain you want, since all the surfer has to do is click on the link. However putting urls in the description box is a dubious idea if you are going the mass uploading route, because it makes it trivial to find all of your accounts (by putting the domain name into the Youtube search box).
In some cases putting a review on root is counterproductive because if your review sucks, you will make less money than if you just redirected 100% of the traffic straight to the sales page. It depends on how pre-sold the traffic is when they click from the Youtube video, and how good you are at putting together a review that converts.
In any case what you are talking about is just putting up a redirect - it's not cloaking.