Which legendary Ephraim should i use? -atk+def or -def+hp

Tough choice, and it mostly comes down to team composition and preference at this point. I'd go for -Atk/+Def so he can deal even more damage with Bonfire activations. That combined with Hone Cavalry and Fortify Cavalry, and he really shouldn't have too many problems.

Ephraim needs his attack more for stuff like Heavy Blade Galeforce with Flame Sigmund, he won't take that many hits anyway.

well... he wil get physical doubles to counter... and he wants atk too...

some of these are superbanes? well he doesnt get hurt too much in terms of atk, his weapon garantees 19MT....

but losing defense make him more vulnerable, he always will get doubled alone... he doesnt fits well with hone and ward buffs due to his weapon, so , evey bane will be fixed by visible buffs... his problem will be ploy teams with gunthra at most.