For a list of Koopa Freerunning WR times and videos, check https://mkwrs.com/smo/ . For the KFRTA leaderboard, check https://www.speedrun.com/smoce#Koopa_Freerunning_RTA .
Note: This route only works if Wooded Kingdom is chosen before Lake Kingdom on the World Map, and if Snow Kingdom is chosen before Seaside Kingdom.
Since timing starts at the start of the first race, the route begins in Metro Kingdom, where the Koopa Freerunning Race takes the longest time to get to from the Odyssey. In the race, the pylon route is used, rather than the IGT WR route.
Next, take the painting to Sand Kingdom, and do the normal pylon route there. After Sand, use the painting to Wooded, then the painting to Seaside, and after that the painting to Bowser's. Then go to Lost and Lake using the Odyssey, and take the painting from Lake to Luncheon. In Luncheon, it is better to not capture the Lava Bubble, and instead to jump up to the second fork, after the first fork.
After Luncheon, take the Odyssey to Moon, Cascade, Cap, and Mushroom (in that order), using the WR strategies there. After Mushroom, take the painting to Snow, which is the last race in the route.