I don't own any smok mod so can't really say anything (i also don't care for "fit" and wether my tank has overhand or not) all i will say is that i was gonna get myself a serpent smm since it's the most noob friendly rta i've been recommended (can you tell i'm also an rta newbie XD) i'm by no means a cloud chaser, fact is i barely go above 35 watts atm so i'd suggest you go into the rebuildable sections for better suggestions.
NB: same answer for your rdta,can't say since i don't own any rtas atm only rba i own is my big baby beast which i really don't like much but i need it to vape my gunkie juice.