Darlene, I'm very sorry for your loss, and am happy to hear you have adopted another cat!
Our experiences, for what it's worth:
When we decided to get a Savannah (about nine months ago), we shared some of your concerns. We have a very affectionate and somewhat dominant male cat to consider, as well as a shy and skittish female cat. Both are about four years old now, and they were our primary concern in adopting a Savannah (or any other cat, for that matter).
Both of our cats are rescues and we wanted to make sure we adopted a kitten who would fit well into our family.
In the end, after lots of conversations with breeders, we chose a female Savannah who has been a perfect addition to our home. Our male cat has "adopted" her like she is his personal baby kitty, and our skittish female tolerates her as well. All of the cats get along (for the most part) and nap together, play together, etc.
Monkey, our Savannah, is an F2 with an exceptional personality. She has energy and can be "destructive" where paper towels and TP are concerned, but she's really just a super curious, smart cat who approaches everything she does with a lot of enthusiasm. She has plenty of moxie and isn't afraid of anything - but gets along just fine with our super shy, skittish female cat. There's no intimidation, etc. going on.
However, perhaps most importantly, she's an individual, just like our other two cats, and Savannah personalities seem to differ as much as personalities do in any other cats - or people
Regarding the size question, this is not something we particularly cared about. To be honest (and I'm sorry if I offend anyone), I don't understand the obsession with size. Our first priorities were health and personality, and the emphasis our breeder put on socialization.
That said, Monkey likes to weigh herself by sitting on the bathroom scale (!), and her last weight that we saw a few weeks ago was 10 pounds (at about 11 months old). She is long legged and petite, and absolutely perfect just as she is.
My strong recommendation would be to spend time talking with your breeder, meet the cats via Skype or YouTube video if you can (or visit if that's possible) and prioritize health, socialization and personality above all else
