There's no need to do a secondary racking at all. You are correct, if it sits on the yeast in the primary, it will only improve. I'd let it go about three weeks in the primary before adding any adjuncts to the beer. If you want to add vanilla bean, simply hose it down with sanitizer (star san) and split the bean down the middle to expose more vanilla surface area to the beer before adding it. For a five gallon batch, that'd be about two vanilla beans for sometime between a one week or two week soak depending on how much flavor you want in the beer.
Oak chips are tricky but here's the best way to do them. Remember this advice, it's best to under-oak your beer than over oak it. Oak chips have a lot more surface area than cubes, plugs or spirals so they will oak your beer much faster. I like to use light toast American oak on my beers. Take one ounce and soak it in your favorite bourbon in a mason jar for about a week, between week two and three during the fermentation is fine. Get a sanitized nylon hops bag and put the oak chips into it so they don't float all around the beer. Oak chips can be dusty and fine and difficult to get all of the bits out without a secondary racking, but secondary rackings are one more level of potential infection and oxidation problems. Toss the bag of whiskey chips into your beer and re-seal your fermenter lid and airlock/blowoff tube and let it sit in the beer for about two days. At two days, use a sanitized turkey baster to start drawing out small tasting samples. Taste the beer. When it has the right amount of woody oaky bourbon flavor in it, remove the oak bag and bottle/keg the beer.
DO NOT USE THE "TOSS & PRAY" method with oak chips. If you toss it in there and think, "Oh, i'm going to let it go for two weeks" and forget about it, you're going to wind up with a vastly over-oaked tasting beer. It will take well over a year for that oak flavor to fade out of your beer, long after the hops and vanilla have faded out of it. Trust me. I speak from experience. Start tasting at 48 hours. If it tastes great, pull the oak out and bottle. If it's not quite there yet, let it go another day an re-taste.
Good luck.
