If they get too wound up and keep coming at you, then yes, remove yourself from the playing field. Two puppies, yes it is twice the work (as in clean up) and expense; but that is the least of mine and others' concerns who often advise against. In far too many cases, adequate training is not provided because the puppies have each other for entertainment. They have each other for company (something I believe you mentioned as a consideration for getting two), and humans take a back seat.
Key is going to be giving them each individual time and training. They can still go and do things together, but make the point of individual trips as well.
As littermates, they already have a bond with each other, but DO NOT take for granted they will continue to live harmoniously. Nikki has been lucky so far and she had her girls spayed before hormones began playing havoc. Did the breeder have other females around besides the dam of the litter? Were they all separated or were they able to run together? Females, even littermates, are more prone to take a dislike to each other and once that happens, keeping them separated will be your only option. To be blunt, they don't call them b*tches for nothing! And I've got a couple of Pem girls here that'd I'd match against any Rottie or Chow when it comes to being ready to rumble. Yes, corgis "can" be very aggressive.
Continue to work with them together and separately. Enroll in puppy classes as soon as they are old enough and vaccinations are finished. Have them spayed between 4 and 6 months and you'll be on a solid road to having the companions you want. And in the mean time - lots of patience.
Debbie