A few questions on two puppies!

We just added another puppy to our family, sort of unexpected but we were crazy enough to say yes, we went on a trip to visit family members who also had a litter of puppies, they didnt get to spay their dog in time, and she is a lab/rotweiler cross, she had puppies with an unknown breed, a mutt, who is a cross of a cross of a cross :) so they were giving their pups away to homes that would take good care of them, and they kept telling us we could take one, we were hesitant cause we just got a boston terrier puppy who is now 14 weeks old, the puppy they gave us is 8 weeks old.... we were planning on getting another pup when our boston was a little older so we thought why not take a puppy cause while we were there visiting for the week we sort of got attached to one of the pups and our boston got along well with the puppies. The question is our boston and the new pup play and sometimes it sounds like they are really fighting, growling and barking, is that just playing? we've been separating them when they do this but we aren't sure if they are just playing or not??? second quesiton: while i'm at work I was wondering if i should continue keeping them together in the kitchen or keep them in their separate crates, i have kept them in the kitchen to allow them to play with each other while we are gone until i get home at lunch, but I'm sort of not sure if that is a good choice? third question: our boston is paper trained should i paper train the other pup, she has made a few mistakes in the house but is doing well going outside but I don't know if she will pick up the same habit as our boston, who actually only goes on the paper when he really needs to, i take them out for regular walks, they tire each other our during the day which is another reason why we wanted to take her cause our boston has sooooooo much energy... sorry for the long post never had two pups at the same time.... it's actually a lot of fun, cause the boston is sort of trained knows his basic commands, i just have to work with the other one.... how does everyone else handle having two pups at the same time......Thanks!!