i got to hold a friends pups at that age but i dont think in general breeders alow it they are normaly 3 weeks before you can handle them.
if snuggleing into your chest is a sine of agression i think every cockapoo on this forum is agressive.
at this age i woul;d say its not possible to comment on their charecter.
can i ask where you red this about the runt, normaly what is said is you dont go for the overly confident pup or the pup that is hiding in the corner. but even then i cant commet as i have never physicaly picked from a litter. its alway been photo or the breeder picking Inca as a contrast to Gypsy.
i would say give it a couple of weeks before you make your final desision. even tell the breeder you have interest in two of them but want to wait to see their charecter before you make a desision which one to go for.