To echo what Peter said, Taylor, GEDmatch will not only allow you to bring your autosomal DNA results into WikiTree to give you another way to find possible associations to others, but starting about seven weeks ago it also began giving us an automatic way pull a link to your compact tree from WikiTree into GEDmatch. Quoting GEDmatch:
A manager of a WikiTree profile can add a GEDmatch kit number to the profile of an individual. On a periodic basis GEDmatch acquires from WikiTree the WikiTree profile information to create a link to that profile and the GEDmatch kit number recorded in the profile. The WikiTree link information for this profile is then added to the information associated with the kit on GEDmatch.
This is extremely beneficial because an active "Wiki" links shows up beside your GEDmatch ID when people find you as a match. Gives them a simple and instant way to browse your tree here to see if anything--er, anyone--rings a bell. To take advantage of this you'll need to check your preferences on GEDmatch after their periodic batch runs find your WikiTree profile. So wait a couple of days (I don't believe we yet know how often these batches are run), then:
From the main GEDmatch page after you log-in, on the left and down the page a bit is an item labeled "EDIT or DELETE your DNA resource profiles." Click that; scroll down to see a table labeled "Your raw DNA kits."
On the line that shows your primary kit number you'll see, at the far right, a button labeled "Select." Click that, and then click "Edit" at the bottom of the table. Look for the section that contains "WikiTree Link." Select "Enable even if alias." That will allow the two sites to synch even if you used a different username for each...which I always tend to do just for a layer of digital security. Click "Save Changes," and, Voila! You're done!
As to the ethnicity estimates you see from AncestryDNA (or any testing company, for that matter) they're as much art as science. They're mostly quite good, but you have to take the results with a small grain of salt. The data are derived from various databases of tests of umpteen people, then run through public or private algorithms to arrive at the estimates.
For fun, once you have your GEDmatch account, explore the "Admixture (heritage)" tool. You'll be asked which "project" you want to run your DNA through and you'll see seven different options...with other options under each of those. Based on your Ancestry report, try "Eurogenes." Enter your kit number and you'll find 13 different schemas through which to view your ancestral ethnicity. Experiment at will. What it will show you is that there are multiple and varying ways to estimate ethnicity. :-)