Hello it's Coolyoshi here and I figured out a route for 100% to get through it quickly while still being able to go fast.

Here is what you can do: -Go to time trials first to unlock Funky Kong by unlocking 4 fast staff ghosts (I use Donkey Kong, Flame Runner to do Luigi Circuit, Mushroom Gorge, Toad's Factory, and DK Summit). I think you can do this faster just getting the fast staff ghosts all from the Mushroom Cup but the time you need for Moo Moo Meadows is really strict which is why I do DK Summit in place of Moo Moo Meadows.

After you unlock 4 fast staff ghosts go back to the license screen and then come back to the main menu to unlock Funky Kong. This will allow you to use the fastest character for all future races (including time trials) which will be overall faster.

After you have Funky Kong you want to ideally 50cc cups first so you can reset if you get bad RNG there, but also to open up all of the time trial courses so you can do those next.

After you do that and unlock all fast staff ghosts, you can get do 100cc cups followed by 150cc cups, and then finally mirrored cups to finish off the hard part of 100%.

Hope this helped!