Disclaimer: Before I start, I want to let everyone know that I have never owned a smartphone, any of these screen protectors or any of these cases. That said, I have been researching this stuff obsessively since I first heard about the Motorola Droid last year (I'm serious about the obsessive researching).
Screen protectors:
I've done waaaay to much research on the whole screen protector subject b/c I thought I was going to get the Incredible. Anyway a very brief summary is in the last paragraph of my post here:
http://androidforums.com/motorola-droid-x/110677-screen-protectors-gorilla-glass.html#post1040420
One thing I didn't address was
glare and smudging: the screen already has glare and is prone to smudging. You won't find a screen protector that completely gets rid of the glare or smudging without sacrificing clarity. This makes sense if you think about: the light is obviously being refracted or diffracted (which of those is right word physics people?) by these screen protectors, instead of being reflected by the screen. Well guess what, it does the same thing to the light beneath the screen protector it too (the screen). If you can live with that (and some people can), then go ahead and look at the anti-smudge and anti-glare protectors. Otherwise, accept that the crystal clear types may reduce glare a teeny bit and they won't mess with clarity if you apply them correctly. They also make smudging easier to clean.
Just a little warning (please don't yell at me for this) but
ZAGG Invisible Shields seem to get the most complaints of any protectors. They seem to be thicker and may offer more protection but apparently they also are sticky and hard to drag your fingers across. Additionally, they tend to have the orange peel effect and there are a few other issues I'm forgetting currently. Your experience may vary obviously. They also are relatively expensive. I personally have a sneaking suspicion that this company has focused more on grabbing agreements with retailers and employed the "show high prices to imply quality" marketing strategy (you'll notice there are FAR more coupons for this brand floating around than any other brand).
Verizon cases:
As far as cases go, if you are an early adopter and need a case right away, I think the
hard silicone cases are the overall best pick. They aren't to soft and rubbery, yet they provide quite a bit of impact protection. They are also quite thin. They don't cover much of the front of the screen but they do rise above the screen: this will provide some screen protection if the phone is dropped face down b/c the case should hit first instead of the screen. The only real complaint I heard from the Incredible forums was that it would sometimes mess with a screen protector and make the edges peel up: this issue wasn't reported very often.
The verizon case with the kickstand is also very appealing given the large screen on the Droid X: you may wanna just set it up and watch some stuff (I know I do). I may be wrong but I think that case is leather. Given that is has room to store a kickstand, it will most likely be thicker than the hard silicone case. I'm not sure but I believe that this case is made of leather: not sure how that will rate up in terms of impact protection.
The holster/shell combo cases are pretty sweet b/c they don't have a clip in and are easy to get off your hip quickly. They look good and seem to fit very well (this doesn't mean the other cases don't fit equally well). The shell parts are extremely thin, hard plastic, so they won't provide as much impact protection as the hard silicone cases. Also you should consider that the they don't cover as much as the hard silicone cases: that may be good or bad depending on who you are. I'm not certain about this, but I don't think they rise above the screen on the front, so if you drop it face down, it will likely impact on the screen itself and not the shell. One more thing that I can't confirm, but have read in the other forums: apparently it's relatively easy for the phone to fly out of the holster accidentally b/c there is no clip (a few people accused those reporting the problem of putting the phone into the holster upside down... there was no response).
Non-verizon cases: (these are for later adopters or people committed to wait for third party cases)
The Seidio Innocase II seems to be a hot pick for people for a few reasons. 1st, it apparently provides wonderful impact protection in a very thin case (perhaps not quite as thin as the hard silicone case from vzw... don't quote me on that). 2nd, it has a seam in the middle that allows you to pull the phone out of it more quickly and painlessly than most other cases that are a single piece. They look and feel good in the hand. They seem to be the quickest, high quality after market case to hit the market after phone release (this was the case with the HTC Incredible at least). These cases tend to be more pricey than the verizon cases.
The Otterbox cases are also an extremely popular and well know for the mind blowing protection that they provide. I believe some of the styles come with some sort of screen protector as an added bonus. The quality of these cases is about the highest you will find, hands down: the prices certainly reflect the build quality (aka they're high). I hear a lot of people saying that these cases are somewhat thick: I won't comment on this myself b/c I'm not familiar with all the different models, but I will say that many of the Otterbox cases have multiple layers which would seem to support those claims. These cases are also notoriously slow to make it to the market after phone release. You will have to be a later adopter or just truly committed to holding out for one of these if you do adopt early.
Hope this helps. Feel free to ask questions.