Welcome. I have a 2015 750, and I love it. The 2015 Streets do have a recall on fuel pump for those built in first 10 months or so, and to add a rear reflector when the factory one did not meet gov size requirements. I never heard of a brake recall for the Street, but you can go to HD web site and enter VIN to see all specific recalls for your bike, and if they are open (still pending) or closed (performed on that VIN).
Since you said you were a new rider, I will share what I learned from a couple of veteran riders. If you have not done so, stop in to local dealer and introduce yourself to service dept, get a card for the service mgr and ask about what service they recommend now. They will register bike VIN to you in the dealer network and check for any recalls. They should also be able to see if bike was ever serviced at any dealership. HD service is expensive to do 1000 mile checkup or other recommended checks at the dealer, but something to be said for working with those who have dealer problem solving computer database and trained techs. If you don't have problems at 1K, 5K, 10K, etc, maybe you have a local shop that will be cheaper for scheduled maintenance. Dealer will probably try to sell you an extended warranty as that is a primary way for them to make money. For a cheaper used bike, it is probably not as good a deal as getting coverage on a $20k bike, but evaluate costs vs your needs. Also good to ask your local dealer if they have a rewards points program as most do, and get them to sign you up before you spend any money on service, parts or clothes. Also ask dealer for a parts catalog, and then you can browse what is available for street, and as multifit for any bike.
I agree the mirrors did not work to see traffic behind me so I added the extenders that moved them out 2 inches or so, and now they are fine. These were the ones I got on ebay $21, because the Genuine HD parts were $60. They are not street specific, being designed for Softtail or Dyna, but they work. Tip go to hardware store and get some lock washers (stainless so they dont rust, and because I could not find black ones). Use them in between every screw and nut so mirrors don't get loose while riding. I'm also going to locktite mine now that I have them positioned where I know they work. Very dangerous if they flop around and you cannot see.
Last thing to know for first year streets is that a lot all of them have had a failure of the woodruff key that holds the alternator's stator to the shaft on the engine. So if your 2015 Street XG 500 750 ever develops a problem starting, won't start, or wont stay running. Turn it off and don't keep trying. Ask your dealer to pickup (It is too dangerous to ride a bike to the dealer that may stall in traffic and not restart). The woodruff key has probably broken and the stator is spinning on the shaft throwing off the electronic timing so engine wont spark at right time. Don't let dealer techs try to keep starting after you explain and they try it once. You may be able to save $300 stator if broken key has not already damaged it. Ask them to take left side engine cover off to diagnose if stator rotates loose around shaft. One tech was not familiar with this problem and told me every reason under the sun why bike would stall until another tech suggested this was a known problem in HD service database for 2015 Street. Another symptom is if you hear a metal part rattling/tumbling on lower left side while riding. My key split and rattled around until it destroyed the stator part, then bike would not start or stay running later that day. Fortunately dealer fixed for cost of parts (bike was past one year warranty). This is a known problem on 2015 year Streets with a bad supply of woodruff keys that were not heat treated well but no recall was ever issued. One tech said every 500 in their riding academy fleet had this problem sooner or later. This forum has several threads that mention the problem, but this is a concise summary.