Fleet Feet 20%

Felt like 20% and did tests that concluded 20%. With an elf its less noticeable to feel 10% vs 20%.

But you are correct, Since I have data from commerce that concludes Nimbus Speed = Fleet+TS20 on cart.

This would be 1.88 x 1.6 x 1.1 = 3.24676

Additionally, your first video is calculating 15%, which is also wrong amusingly enough.

A better way to confirm this is having someone with Fleet feet run side by side with someone with a Floral Fairy. Make sure the race is the same. At least the buff from Floral fairy is confirmed 10% if I am not mistaken.