The hand positions depend on the type of bike..I always try to keep close to the road positions on my bike so I am building the core musles for road biking.
Some spin bike you can and some you cant..When you stand use the position keeps all of your weight on you legs..My instructor says you should be able to feel the seat when you stand.. To know for sure try no bounce where nothing moves from your waist up. All action and strength comes from lower body. Do that off and on for a whole song and your thighs should be singing the blues and getting tight....