a.) If you are going light, I would recommend light hikers - low or ankle cut depending on your preference. However, things will get wet and muddy so you might want to consider wearing a waterproof sock with a non-gortex shoe or a gortex shoe. We had rain for most of the trip, and my GTX Montrail Hardrocks did great until the very last day and then they started to wet through. You really do not need a heavy leather (or similar) traditional backpacking boot on this trail. It will only be a hindrance on the beach.
b.) Wildlife - whales, seals, sea lions, bear, cougars, wolf, mink, bald eagles (lots this year), and sand flies. Most of the sealife is visible toward the north of the trail. I did not see any bears this trip but have in the past. No cougars visible but we did see some tracks. Many wolf tracks which was a thrill.
Each designated campsite has bear lockers or a means to hang your food and smelly toiletries.
Water is abundant and clean. You would be fine to use chemicals v.s. a filter.
Use trekking poles! They are invaluable on this trail in my opinion.
Take your time as things are always slippery.
Have fun on the ladders!
Any other questions, please let me know.