In these kind of games, tap is usually the better choice because it is much easier to tap the virtual directional buttons than tilting the device. However in Water Slide 3D game, tilt is better than tap in terms of avoiding obstacles and being thrown in the game. This is because when you choose "tap" as you're control preference, your handling or the "speed" of changing direction is much slower than in "tilt" control mode. Choose Tilt to have better handling and Tilt is much more fun to play than the traditional boring "tap" control.

There are only 2 kind of currency available in this game: Coins and Gems. Gem Items/Upgrades are far superior from Coins Items/Upgrades. However it is difficult to obtain gems for free but you can purchase them via IAP. If you don't want to spend money to get gems you can use your coins to buy items and upgrades. Buying Items or Upgrades that cost coins is difficult if you don't know how to be a cost efficient buyer. It is recommended to buy an item in it's category eg. "accesories" that has the maximum value. If you can buy the best item in that category directly without purchasing it's cheaper alternative then go for it. Here is a suggestion of items and upgrades that cost coins for cost efficient buying. Important: In order.

Frog Feets (Accessories) Cost: 10k.
Gold Man (Character) Cost: 25k.
Shield (Upgrades) Cost: 500->1.5k->3k->6k->12k.
Magnet (Upgrades) Cost: 500->1.5k->3k->6k->12k.
Speed, Handling, Acceleration and Stability:

Speed: Maximum speed.
Handling: The ability to control your character easily.
Acceleration: How fast can you get to the maximum of your speed.
Stability: To stabilize your character on sharp turn and to avoid being thrown at the water slide.

All for attributes will help you attain 3 stars in each levels. However it doesn't mean it will make your gameplay easier. Speed and Acceleration attributes has certain advantage and disadvantage. If you are collecting 3 stars then those 2 attributes are good to improve however if you are collecting coins then those 2 attributes should be avoided. For stars you need to have speed and acceleration to meet it's star requirements.
Improving speed and acceleration will make your gamplay difficult because it adds pressure to avoid obstacles or being thrown. If you are collecting coins then your priority is to stay alive and complete the level to get more coins. Remember each level will cost 1 energy to be able to play. You need to collect coins as much as you can for a single energy. Handling and Stability are the best attribute you can improve if you are collecting coins as much as you can. You should avoid obstacles and being thrown so "speed" is not important.