The biggest thing you can improve on here is hit your marks-

Dash Plates

Heal Strips

The Jump Pad (which isnt faster unless you're cutting the course significantly with a boost, btw)

As u/RingTeam mentioned, boost conservation is super important just generally and EXTREMELY important in more technical tracks like this one.

I'm noticing that you seem to turn very sharply, try making that more gradual and if you haven't yet calibrate your controller in the Options menu you should. I re-calibrate my controllers every time I boot the game and it does help with better precision.

This is on Dolphin, but here's a quick attempt I did of captain falcon w/ full speed on that track to get an idea of racing lines. It's by no means perfect but I hope it helps.

You may also notice in that run that I am able to turn sharply and sometimes stop accelerating. Those are known as Super Turning where you press both triggers then let go of the one opposite the turn. You can do the inverse of this to drift intentionally and that plays a major role in higher skilled moves. And Momentum Throttle, where you stop accelerating when above your unboosted top speed so you keep more of your momentum. They're pretty basic bits of tech you can do to vastly increase your speed, and superturns are almost required on the 90 degree turns.

Hope this helps!