Hi - The short answer is no, you won't automatically get lymphedema from having nodes removed.
Now for the long answer: I had sentinal and 12 lymph nodes removed 4 years ago. I remember being concerned about lymphedema. I am still concerned, but it's nothing I worry about. I don't know what a two scoop mastectomy is. Do you mean bilateral? Are you having nodes removed from both sides?
If you're having nodes removed from just one side, be sure that in the future all blood pressure, blood draws, injections, etc are done on your other arm. Even when I was in the hospital, a lab tech came to draw blood from my mastectomy side arm and I had to remind him.
I did initially have some swelling on my left (cancer) side - not in my arm. My radiation oncologist sent me to a lymphedema specialist (physical therapist). She showed me exercises and massage to do. She also fitted me for a sleeve.
In the beginning, I did the massage and exercises religiously. It's been four years now, and I don't have lymphedema. I am careful about wearing gardening gloves, wearing my sleeve when I fly, and treating any small cuts with antibiotics immediately. I will always be at risk for lymphedema, but so far I have dodged it.
Best of luck with your surgery. I will be thinking of you.