asmin There are Trans guys that present as men and some pass even pre T. So i would hazard a guess that similarly a trans femme would be able to boymode given blessings of genetics and a keen fasion sense.
Additionally most transfemmes would have their voice at their disposal should they want to add touch to their boymoding. (Since voice is not affected be E the way it is by T).
Note that gynomasticia is not that rare and quite a few men especially of larger size have visible .. chest fat, so even having modest breast development shouldn't be that much of a hindrance to boymoding i would guess.
Point of note, dressing/mannerisms goes a long way. Before all the modern magical (um.. medical) interventions were possible people used to still be and live as trans persons some even stealth, so i think this certainly possible and one may try seeking tips from trans guys in this matter.