i use the lr and photoshop cc combo which includes a few other products as well like bridge, camera raw of course, etc.. It works the same as if you own it. You store your images where you want them. I store mine on my hard drive.. as an option you can store online. They do "check" your machine to a) make sure you are paid up and that you are following the license agreement.. which I believe allows you to install on multiple machines ie a desktop and a laptop but only use one at a time. There is a newly released feature that provides lr on an ipad (I have an android tablet) so I haven't been able to try this. I know you can download photos from your camera to the ipad and access and even do some PP on the ipad. Rumor is they will be releasing an android version at some point. I've been using this for a few months now and have received at least 2 updates / new features and camera raw update already. So as long as they keep the price point at $10 per month... I'm good with it. The main issue, is that if you let it expire you no longer would have access to your image pp modifications. So make sure you backup your catalog and smart previews (LR) so that if downline you choose to buy vs rent you can recover your pp updates in LR. similiarly if you save psd files in photoshop You should be able to use a purchased copy of PS if you choose not to rent.

70-200 L either 2.8 IS or non-IS or F4 are all great lens and with proper light all have excellent IQ. You have an excellent camera (same as what I have) and the camera itself works wonders in lower light situations so do not be afraid of the F4. I personally have the 700-200 2.8L and also the 100-400L, I find that I consistently grab the 100-400L more often because of the extra reach (being the 5D3 is a full frame). IQ on the 100-400L is absolutely great but if there is a shot that I absolutely need to turn out well, well then I grab the 70-200L. It is almost impossible to shot a bad shot with it, the only issue is it weighs a ton. My friend has the F4 and its weight is just about perfect and like I said image quality is exactly what one would expect from an "L" lens.

If I was to do it over I think I would go with the F4 or 2.8 non-IS just because of the weight difference. I guess it all depends on what you want to use it for and for how long you will be holding the equipment at one time.

You ask about "L" lens vs other brands. "L" lens are made specifically for the Canon camera by the people who make the Canon camera, they are the experts. The lenses cost more simply because they are worth it.

Your 5D3 cost a small fortune why would you even consider lowering its superior quality but trying to save a few bucks? You did not buy your camera to take nice shots, or good enough shots, you bought it to take the best shot. Am I right?