They’re the same edition.
You can just use the blade cantrips, because Tasha’s is completely legal and compatible with the OneDnD playtest rules.
And it’s a playtest. There is no “edition thus far”.
Lastly, they clearly stated that the playtest early on at least is only featuring spells that are in the phb, so the absence of a later published spell does not mean it’s absent, and that if something isn’t mentioned in the UA documents at all, it should be treated as unchanged from the existing rules.