I wore road shoes when I did it, ok weather was kind so not really any muddy issues, I used the same pair just changed socks regular.
Lake - It is your choice but I personally would advise against doing all of the route.
I found on the whole the route fairly boring after you have seen x amount of bridges and barges it all becomes very samey...
However I would recommend running what you perceive to be the night section for you, I did this and it did help no end having that prior knowledge. I was lucky though there was a race called Ultra 90 which went from Northhampton to Tring on day one and then back on Day 2.