I think Gal will do fine as Wonder Woman. Sure, a little more muscle mass would've been nice, but to me Wonder Woman has been her best when she's been shown as strong AND sexy -- and, in my opinion, too much muscle on a woman is a turn off. Besides, the first Wonder Woman I ever loved - portrayed by Lynda Carter - was anything BUT muscular.
As far as Jesse Eisenberg's Lex Luthor, I think his portrayal will be an evolutionary one into the Lex that we've all learned to love to hate. I'm interested and excited to see where he takes the character. I think he will lose his hair as a result of radiation poisoning from overexposure to the Kryptonite.