There are no "Adobe free stock videos". And you can't use watermarked assets except for preparing your work to show a client prior to buying the asset. All other use would consist a (c) infringement and could expose you to (c) claims.
This is not only true for Adobe, but for all stock footage providers. You need to acquire the license to use the data.
What @Abambo writes is still true for all paid Adobe Stock assets.
However, the good news is that there are now indeed free Adobe Stock videos – many of them – which are unwatermarked and free to download & use for most purposes. More details here:
(These are part of the new "Free Collection," which is now up to over 500,000 assets of all kinds.)
Regarding YouTube, note these licensing terms for all Adobe Stock videos:
I wasn't aware of the free stock video collection. I wouldn't, however, use the watermarked version here, as this looks like unlicensed assets. And for sure, free does not mean rights free, so you still need to follow the licensing terms, which is for video probably more forward than for image assets as the licence type coming with the asset is enhanced.