The video wasn't clear because it was only tested with vanilla Shulk stats. Speed Shulk has about the same air mobility as Jigglypuff, so we can use this to our advantage to escape Fox's jabs (they don't have the "trapping" knockback like Link's does).
It's actually quite the opposite. Monado
Shield just makes it easier to get combo'd by Fox.
For example, in shield, you might be able to get to the ground faster at 0% to ~15%, but you're going to get grabbed if you shield, and good Fox players are going to expect that. Fox's U-tilt, for example, does a very good job of juggling characters, especially the heavy characters with falling speeds like Bowser, Dedede, and C. Falcon. The Fox player also isn't restricted to U-tilt over and over: he can just as easily shield or turn-around grab.
Either way, Fox can trap heavy opponents like this by micromanaging to their options this way, which is why I think being in Shield is a bad idea as you'll get trapped in his barrage. Like I mentioned: D-throw -> F-air -> U-air is 32% and a true combo between the F-air and U-air. Here's the combo in action vs Falcon at 10%:
Not necessarily. Fox's 2nd jab has more hitstun in this game than it had in Brawl, and also, there are additional frames of landing lag after landing from htstun. If you watched the Link jab trap video, the part that explains how the trap works regarding landing should answer that:
http://youtu.be/fWmtA1VCHWY?t=1m16s
The same applies for Fox's jabs: there are a few frames of landing animation that these characters have to go through.