Does regular Farfetch’d gain the defense boost from Eviolite, or does it need to be Galarian form? Same goes for Linoone and Mr. Mime.
No, it doesn't.
A Pokemon only gets the Eviolite boost if it itself can evolve.
A regular one won’t get the Def and SpDef from eviolite, only the Galarian Form can seems it will evolve to Sirfetch'd which was a Pokemon that introduced in gen 8.