Is it safe to perform a trick after the ramp at Rainbow Road

From the video, it looks like the player does a trick off the final mushroom in the cave to get a boost, does a wheelie, then, just before he hits the grass, uses a mushroom boost. As he's in the air over the canyon, he steers to the left.

Keep trying! You'll get it.

It really boils down to your personal skill, the motion controls of the wiimote make it very susceptible to shoddy performance as it is. Mario Kart Wii supports the following alternative control schemes, all which don't use motion controls:

• Gamecube controller
• Wiimote + Nunchuck
• Classic Controller

Rainbow Road makes liberal use of turns, here your ability to drift makes the biggest difference. There are several places where you need to be able to make tight drifts, and others where you need to make wider turns.

Your setup does matter. Different characters and karts/bikes are going to have different characteristics. Some will be better at turns than others. For example, I personally prefer Funky Kong with the Flame Rider. Others might prefer smaller characters to maximize their handling and acceleration over top speed.

Use your mini-boosts to your advantage. Probably the single most-important thing about the mini-boost is that it straightens out your turn. Letting go of your drift means you're going to be shot in whichever direction your kart is facing, use this to your advantage. For example, in the large 8-section I use it to ensure I go straight across instead of falling into one of the holes.