Perhaps I have simplified this too much. Don't be discouraged, please. My suggestion was based on what I do, having installed a file manager and perfect viewer onto my Samsung tablet.
As I said, I don't know a lot about ipad, never having used any Apple device. However I've been doing a bit of research and I think you should take a look at this site:-
http://appadvice.com/appguides/show/comic-file-readersThe 2 free apps seem ok and will probably work ok for viewing .cbz, .cbr and, I think, pdf files.
The problem with ipad apps is that many of them cost - (hint to anyone tempted to buy a tablet for comic reading, there are many more free android apps offered on Google store) - so you might decide to pay for a speedy, all singing and dancing comic reader. Someone on here must know more about this and could suggest the best to try.
Going back to displaying bigger than standard American comics, with perfectviewer on android, there is an almost invisible, small 3 bar button at the top of the screen when a comic is loaded up. Tapping this brings up a menu and one of the options lets you change the size of the page on the screen. So, the tablet being held in landscape, choosing "fit to width" brings up the top of the page and you can either scroll down as normal, or tap the right hand side of the page which will bring up the next section of the page. Excellent for reading fullsheet comics, French G.N,s and Sunday compilations such as Charlie Chan.
I can't say often enough how easy I find reading comics on my Samsung. Installing the free app, File Manager, lets you find downloads on both the device memory and on a micro SD card, if you have one. Tapping a title and choosing "open as image" will automatically bring up the comic on perfectviewer. This works for .cbz, .cbr and pdf files and pdf files look much better on the perfectviewer pdf extension than on the normal pdf viewers, because you don't have to scroll down and have a bar at the top, you simply tap the right hand side of the screen to flip to the next page.
Curious to read more opinions on this subject as it's a growing part of the hobby.