I love this game so very much, and I'm almost tempted to try routing a 100% category, if I were to go through with it, and that includes, all campaign missions, Gang Hideouts, Criminal convoys, QR codes, Online Hacking, etc. How long of a category would you estimate it to be?

I'm not really sure how long 100% would take. Any% can be done around 3 hours 20 minutes., so that leaves the rest. Online hacking would be very random, and I don't know why you would want do that. There was talk of "offline 100%" being a more viable category. I would put it at over 10 hours, but I need to see a route to estimate more clearly.

Wolfbloxer is actually working on an offline 100% route, but he is currently taking a break: https://docs.google.com/spreadsheets/d/1TmZZ50CYiFBc87ARhnPHDv3oeuoZadONK0lLIgi8Pf0/edit?usp=sharing

Old news now, but the offline 100% has been added and done a couple of times already by @MrDirtbag: https://www.speedrun.com/wd/full_game#100

Route in terms of mission order is done, collectibles have yet to be fully routed. Mr. Dirtbag has a route that is complete to my knowledge.