I've heard of people fat loading for a show, but really I think it's very much an individual thing and should not be followed because one or two guys had great results with it. The default method is carb loading because your body is depleted during peak week, then you carb load to get all of that glycogen into the muscles, hence looking fuller/tighter/shrink wrapped.
When I was on keto for my show prep for a month and a half, I'd call that "fat loading" as my fat intake was the vast majority of my calories every day, and I can tell you I looked lean and hard but most definitely was NOT full, very much the opposite, pretty flat.
Concerning vascularity, most of that will be genetics and how lean you are. Some guys I know are vascular as hell even when they're 30-40 pounds away from being shredded. There are some things you can do to slightly manipulate vascularity, personally I found a rice cake with honey and 1/4TSP salt (the salt being the main thing for vascularity) 15 minutes before pre judging worked very well for me.
Overall if you want to try "fat loading" I'd recommend a trial run before your show, but remember carb loading after depletion Is the standard protocol for a reason, provided you find the right amount of carbs for you.
Some people also use carb front loading, where you get your biggest carbs loads Monday/Tuesday before the show, then adjust throughout the week to fine tune as needed. I don't think there's a right or wrong here, just what works best for most. Personally I don't know anyone who "fat loads."