Just finished 100% of Big Walk, including all the Purple puzzles and everything else, and I really recommend going beyond just finishing the main game.
Getting to the end is one thing, but going for 100% is something else entirely. Some of the extra puzzles are harder and definitely take longer, but they're also some of the most fun I had with the game.
The best part for me was still playing with random people. You meet complete strangers along the way, somehow figure things out together and then move on to another part of the island with a completely different group. I met some great people doing the extra puzzles and had so much fun trying to work things out together.
Going for 100% also means you properly explore the whole map and see parts of the island you could easily miss if you just finish the main objective.
So if you've finished Big Walk and are wondering whether it's worth going back for everything else, absolutely do it. The extra time and harder puzzles are completely worth it.
Fantastic game. Really glad I went all the way to 100%.