'Cam phaser' usually refers to a camshaft position sensor (CMP). In particular, Ford engines where they just removed the distributor, and replaced it with the lower half of one (shaft/gear part) with a cam sensor on top.
He's talking about solenoids and associated oil passages that control the VVT. It makes the engine more sensitive to sludge or debris in the oil, but a higher viscosity should not have an effect...varying oil pressure is expected. Running 5w30 instead of 5w20 would just be akin to the engine oil temp being lower (more viscosity/oil pressure).
Mmmm sort of but not quite...
Remember, we're talking overhead cams here.
The engine actually uses a pulse ring and a pickup sensor that sits behind the crankshaft pulley to determine crank position. The crank sensor is located to the right (passenger side) of the crankshaft pulley down next to the belt tensioner pulley.
Then there are two camshaft position sensors installed in the front cover that sit well.. right near each of the camshaft phasers. The computer uses these inputs to adjust valve timing on the fly.
The camshaft phasers (in the context of the 4.6L 3v) are actually part of the sprocket that the timing chain goes around but they can also advance or retard the cams up to 60 degrees of movement in relation to the crankshaft. And yes, ultimately they are solenoid controlled.
In fact, the phasers can adjust cam position so much that a lot of guys run into trouble when they move to bigger cams so you'll hear a lot of people talking about running 20 degree phase limiters or phaser lockouts which basically amount to a mechanical stop to prevent the phasers from rotating so much.