Eggers you don't say where you are fishing the fish-off or your preferred method of flies, so hard to say, i'd assume it will take place in March ? (as most fish-offs occur around then) small black or brown buzzers should be around in March, so i'd go with those, However (depending on what i see on the day) it could all change. I won my fish-off in around an hour and had to stop fishing, was a long 6 or 7 hour wait to see if i had the heaviest bag.
Oakham is correct about Whacky races at the Final. I fished in the Troutmasters final last year, for the first time, should you get that far my advice is this, "relax and enjoy yourself" it's a good day, and Trout Fisherman pay for it, get a walk round Grafham at least the day before the final, speak to the Bailiffs and anyone fishing, ask them what's doing well, try to pick out a few nice bank spots.
In my opinion you want to draw the bank in the morning session as it's where most competitors in the final fail, i drew the boat morning session,

and had a couple of fish. With that many anglers fluff chucking in the morning, fish may tend to be spooked and move further out making afternoon bank fishing imho harder, you could however head for the dam wall and fish very deep and hope to pick up one or two.
I have no idea if you'll need to use trailing boobies or the bung, (not my type of fishing), but whatever floats your boat, buzzers should be plentiful around that time, and a team of buzzers and nymphs will normally take a fish or three, as an aside i have never seen buzzers as large as i did at Grafham last year, they were huge !!.
My only gripe with the final was, rules state when bank fishing, you should be able to see daylight between your legs, only a couple (including myself) adhered to that rule, everyone else was wading chest deep in chest waders, and the marshalls did nothing about that.
Some people will go to any lengths to win/score points/prizes, fortunately i'm not that desperate.
Like yourself i only fish for fun escapism, and relaxation, Just try to relax and enjoy it, good luck in your fish-off.
Best regards
Jim