-1
Femboy refers to physically effeminate males.
Tomboy refers to females that partake in traditionally masculine activities or dress in male clothing and often interact in a masculine manner, tomboy however does not imply a masculine body build.
Boyish refers to a males physical likeness, or figure that is physically male like, proper terminology on e621 for this would be manly
In short former is dress and personality, latter is body physique, as well as improper terminology.
Updated by anonymous