Well, you really won't need to get into a "whitewater grade" PFD unless you plan to really hit some hard whitewater. The class III you have now should do you just fine. Normally all the difference is the extra floatability you'll have. Which shouldn't be needed unless you're hitting hard water. The extra floatability (is rated in pounds) is good for water that pulls you under. But usually as I said not needed. Plus, there are a variety of vests if you do upgrade. If you're the oarsman, best vest to buy is either the standard whitewater vests WITHOUT the collar, or kayaker's vest. You'll have more mobility with the kayaker's vest. The vests with collars are designed for passengers (will be rated class III/V) and have no mobility. So pluggin the oars all day will make you sore from not being able to move like you should.
First off, what kind of boat do you have? A pontoon grade boat SHOULD NOT be anchored in anything but SLOW current. They are unsafe because of design. But whitewater grade catarafts will easily anchor in faster currents you'd fish in a driftboat. But still, always best to stay away from fast currents, especially if you're still green running these boats. Once you're accustomed to using your knife (you should ALWAYS carry a SHARP one hand opening knife to cut away anchor line with) you can dare the faster currents. I've owned standard pontoon boats and whitewater grade catarafts. The cats will ride high and fairly level, even in currents. The pontoon boats will ride a wheelie. Faster the current, the higher they will pop, and with their low weight carrying capacity, will actually get sucked UNDER if current is heavy enough.
TO answer your question though. I anchor up on head of the pockets if I'm fishing strictly from the boat and have high banks, I'll anchor up in the swifter water above (ONLY do this in a good boat, NEVER in a inexpensive pontoon type boat). I will also fish in VERY wide slots and anchor near the deep ledge on one side and cast into the seam on the other side (hard to explain, more of a deep pocket you can't stand in to wade to fish the pocket on other side). Having a spey will help here, but not alot want or need them. Besides that, you'd only need an anchor if you're running down a river and want to stop and change a setup. I've done that many times when I had my single boat.
"Good angling ethic is not a monopoly practiced just by fly fisherman" - Bill McMillan