Don't use the 5w20. It replaced 5w30 as the factory recommendation only because it gave an increase in Ford's average CAFE numbers. The fuel economy differences are small enough that a single user would be hard pressed to notice.
The kicker is, the testing that Ford did to internally validate the oil showed increased engine wear compared to the 5w30. However, while it may have been more wear than the 5w30, it still was within Ford's acceptable wear limits for thier engine durability tests, so it was approved.
In regards to standard oil vs. full synthetic, meh, it tends to come down to personal preference. Synthetic has a more consistant chemical composition, and less effective viscosity (this is where the increased power claims come from, and there is some small truth to it) but, standard oil is much cheaper, and still quite effective as long as you buy a quality oil (most are at least decent, just look for the API certification label, and try to get a well known brand)
The one situation you want to avoid is to run standard oil for many years, and just switch to synthetic. Engine lubrication will be just fine, but standard oil, with the larger and less consistant molecules tends to swell oil seals more than synthetic will. When you switch to synthetic, as the new synthetic oil soaks into the seals, replacing the standard oil, the seal will not stay swelled up as much, and may develop a small leak. This doesn't always occur, depending on the types of seals, etc. but it is known to happen.
