I made some iconic mules in the past that were 12 monk (abundant step adds so much, though not technically speed), 1 barbarian (for 10% speed), and 2 druid (for wolf). Unfortunately, as mules, they don't really need to go anywhere lol.
My fastest, real life, was a tabaxi monk stickfighter though. Spring attack gives 18 sec of sprint boost, with a 20 sec CD. Couple that with abundant step and monk speed and I fleeeeeeeeeeeeeeeew ahead, leaving my party miles behind heh.
DL technically gets a speed boost after using wings, but it seems like it doesn't actually trigger 90% of the time, so bleh. Same with DDM.