Transitions are important in a race of this length. My bike outfit consists of swimsuit, singlet, bike shoes, and helmet. No socks, gloves, or bike shorts. My running outfit consists of running shoes, swimsuit and singlet. No socks or shorts.
Some people bike in their running shoes.
I think for a hilly course like this that bike shoes are worth the slight extra time of a shoe change. Modern bike shoes have velcro straps, but mine have laces. I use lacelocks on them. I also put elastic laces in my running shoes. The hills make this a fairly serious ride for its length.