What Comp Settings are Best/Flexible for Animated Tutorials 4 Multiple Devices laptop, iPad, and TV?

Question

I'm making animated tutorials on a particular subject.  I will have these on a website and want them to be viewable on devices ranging from laptops to iPads to TV to iPhones.  I believe one approach to setting my Comp Settings for AE is to use a Preset like HDV/HDTV 720 which results in 1280x 720  pixels, 720 pixel resolution, square pixels, and a 16:9 ratio.  The advantage, as I understand it, is that it will work for HDTV and that, if I use something like YouTube, horizontal letterboxing will be the result in a 4:3 format (of course, with black lines top and bottom). 
Unfortunately, this seems to make great sense if the content is, say, from video photography of scenes.  My content is animation and enough text at times to make me think horizontal letterboxing will make that text too small to read... that I will sacrifice some content and quite a bit of readability in such horizontally letterboxed setups.  Am I better off sticking with Comp settings at, say, a 4:3 ratio and accepting the "black pillars" on wide devices?  If so, what should my resolution be and what should the absolute width and absolute height be in pixels?  640x480? 1280x960? Something else?  My main concern hear is that I have enough pixels and resolution so that inages remain clear on TV.
Anything you can enlighten me on here will be greatly appreciated.  Is there a great discussion/tutorial on this somewhere?  Because I'm having the growing creepy sensation that the more movies I make, the more "fixing" I'm going to be needing to do when I start up my website.  Please pull this thorn out of my paw!  Thanks in advance!
I have a MacBook Pro with Snow Leopard... and CS5.5 Master Collection, so I have Media Encoder.  I'm also on Lynda.com every day.  So point me in the right direction and I'll attack.
Road Quill

Answer 1

Thanks Bogie san!  This is a big help to getting me started.  And the link got me a little farther into Media encoder as well as Group of Pictures, intra-frame, and inter-frame.
One more related question... which will no doubt look simple (minded) but have an answer fraught with complexity. 
If you were me (don't panic!), and you're making animated tutorials in AE with lots of illustration (some created in Illustrator and some in After Effects) and a significant amount of text from time to time (e.g., sometimes there are several boxes with, say, five English words in them, plus some drawings in the same frame with the boxes so that, although the frames are not cluttered, I also do not have the option of extremely large font sizes)...
...AND you believe most of your users will view from laptops, from LCD desktop monitors, and from iPads and the like (not iPhones so much)... with HDTV being something you view as an option it would be "just nice to have" though not necessary...
...what parameters would you choose when you set up your AE files? 
As a straw example, lets say I select 640 x 480 (4/3 pixel ratio) because I think, rightly or wrongly, that would be good on YouTube.  Should I double each number, keeping the 4/3 ratio?  Do nothing?  Do something different?  What about pixel resolution?  Am I worrying about this too much?  
And, yes, I did pay attention when you said, "That's not an After Effects topic."  I'm just not saavy enough yet to know what that really means.
Thanks in Advance,
Road Quill