Congratulations on attaining total womanhood!
Just my input on your questions:
Do I need a gynecologist? I was told to go to a gynecologist about once a year, but my primary physician has responded to her transgender patient when I need something, and has helped me with granulated tissue, and taken a culture to check things out, so I really don't see a need for a gynecologist at this point.
When should I stop douching, if at all? My surgeon gave me a regimen that was only every day for a couple weeks, then, as needed from there. There was a time when i was getting some discharge that caused me to use vinegar and/or just warm water a couple times, but I could see how too much of that could dry out the lining, and the problem went away. Usually I just use a tiny drop of Dr. Bonners Castile soap.
Why are our vaginas longer than average? I guess it depends on the depth you want to attain, and how much skin you give the surgeon to work with, and your feeling on skin grafts. Plus, a natal female's vagina is able to stretch when being penetrated.
Asymetries during swelling? Others have answered that better than I can.