Oh come on, 20 isn't old enough to juice? 23 is? I think it's ok as soon as your growth plates have closed, and by 20, they have certainly closed.
As for cutting, I think ox is the best for that for various reasons. However, that's probably too pricey.
With the 3 you mentioned...winny, eq, and deca...I'd say you could get away with just eq with less sides. If it were a bulker, I would not recommend an eq only cycle, but all you are wanting to do is hold onto muscle. Here's my thinking...deca opens a can of worms in the sides department. You don't know if you will be predisposed to prog. gyno. You don't know if it will kill your ability to use your fuckstick. Winstrol (winny) also has a rep of killing your libido as well as your joints. And if your joints are killing you, you won't work out. Deca helps the joints, so that isn't a bad combo, however it's a double whammy on your wang.
Eq only alleviates this problem of libido. You won't get super horny off of it like test, but it won't leave your dick in the dirt. It doesn't kill your joints like Winstrol (winny). And it doesn't aromatize as easily as test or dbol. It preserves muscle very well as well. Not to mention an eq only cycle will be cheaper than winny.