Hey Joe,
Welcome to the forum. Yes, there is a lot of information out there about lowering and suspension in general. I'll try to answer as best I can for ya.
First off the H&R springs are a great choice. A lot of people are running them and seem to be pretty happy with them. The spring rates are about 10% stiffer than stock.
As far as your concerns for rubbing: Your wheel size is pretty safe as is the offset with the +42. You should have no issues rubbing the tire or the wheel on any of the suspension components or on the fenders. Rubbing or scraping other parts of your car on stuff you might drive over is another story. I am on a similar drop and haven't had any issues yet. That said, be careful on speed bumps and very steep incline/declines you might run into. Like a very steep driveway for example.
If you are going to run the drop springs on your stock struts they will wear them out much quicker. I can't give an exact number because there are a lot of variables like road conditions, driving style, how much you drive, and so on. But do expect them to wear out sooner than they would if you didn't lower the car. Ex: My stock struts were done at 70k. Like horribly done. Should have been replaced sooner.
Also - from some other users on the same springs, you will be sitting on the stock bump stops. Do not trim them unless the spring manufacturer states to do so. You will probably want to look into upgraded struts in the future. Currently there are a couple options available from Koni. Redshift motorsports is a great place to start looking and getting information about what is involved with that. Eventually there will be more options for bolt in replacements. Probably the Tokico Blues will be the other option. Right now just custom fabrication for Koni Yellows. The Orange Koni STR I have not seen in a 2012+ fitment yet.
http://www.redshiftmotorsports.com/RedShift2012CivicSuspPackages.htm
Camber: A very subjective area. Your alignment should reflect your usage and intended goals for the car. You can get a very safe factory alignment or a performance alignment. Camber bolts and arms are not needed but are recommended if you want to have control and adjustability. With any drop I would suggest at least getting the rear camber arms. As you lower the car, this particular suspension design, you will not gain any negative camber in the front but the rear will increase the lower you go. Any drop over 1.5" will probably put you into a significant amount of negative camber. We're talking like -2.5 degrees. Certainly camber does not destroy tires as bad as toe, but it is something to keep in mind. Also camber will seriously effect the handling of your car.
Camber arms for the rear: Godspeeds seem to be the best deal right now. Price wise. Most are identical to each other. I have a set of Skunk2 which I am pretty happy with so far but the cost twice what the godspeed arms do.
Camber bolts: Ingalls/SPC/Whoever - they are all the same just make sure they fit your car. There are two bolts in the lower strut to attach it to the car. One set of bolts will replace either the upper or lower. One should give you plenty of adjustment if you want a performance alignment.
Hopefully that answers everything for you. Let us know if you have more questions.