The VX is actually designed by the same designer that did the Viper, so yes they are similar. But the VX is a significantly different boat with a lot of refinements, some of which were issues with the Viper, some just new.
It does have a drop keel that if I remember right makes up about 1/2 the total boat weight. It also has a turbo package that allows you to take the keel bulb off and turn it into a trapping boat... I have never sailed it this way, but they are less than 6 months old, so as soon as the local vendor gets back from the Olympics I will start harping on him to try it out.
The bulb adds a lot of righting moment so drew weight isn't much on an issue. The rest primarily comes from the hull shape. Once the second chine is in the water the boat doesn't heel anymore, and even up to then it is debatable if hiking really helps. We haven't noticed much of a speed difference, except in very light air, when trying to heel to to leeward.
I have sailed the boat with between 2 and 5 on board, never solo. But ther ware so few strings, and since hiking isn't really necessary I think it would be a breeze. Tiller in one hand, sheet in the other... The spin is launched by pulling one line
, and douced by pulling the other end of it.
is a pretty small non-overlapping sail, and while racing is trimmed heavily, for solo sailing could just be set. Eased when the chute is up and trimmed in when it's down.
Right now the fastest I know one has gotten up to is by a local guy who races A-Cats. He is about 150lbs, and his wife is about 85. They hit 17kn in 20kn of breeze, so I don't think solo weight would be a major problem. Sadly I am close to that alone.