I'm pesadissimo, blue belt. Couple of observations - firstly, competition wise basically first guy to get and hold a solid top position is gonna win. Nine times out of ten, anyway, and bear in mind there is an exception to every rule but this is just generic advice for most super and ultra heavy competitors. Fast explosive side-control escapes are critical, don't let them stabilize or you're fucked. Don't anticipate a high level of guard retention, just smash pass or over under pass, get to side control and switch between there and scarfhold if he keeps trying to get out, snatch a sub when it comes up. That ought to get you through early days competing in white belt super- and ultra-heavy anyway. Shit's gonna change up quite a bit at blue, especially against higher level blues. And every time I watch the purples and up at my own weight class (pesadissimo/ultra heavy) their Jiu Jitsu for the most part looks as dynamic and fluid as any other smaller guy's does. So this is my advice specifically for where you're at for the next year or so basically. Learn how to constantly give directed, concentrated pressure from various top positions and use it all the time. Get to top, take the wind out of his sails, attack him when he's tired, collect your medal.
Take it with a gram of salt too, I'm only a blue belt competing in regional and local events, not some world-class expert or nothing.
Jiu Jitsu wise, overall, I personally like to spend tons of time developing an effective, fluid and dynamic guard. I'm now starting to use some stuff in competition and getting comments from other guys in my division that they'd never have expected it or seen it coming. I like to play bottom positions as much as possible when rolling smaller guys, and especially shite like "pass or sweep" with the really nimble guard passers. Pretty much constantly work the weak areas in your Jiu Jitsu, and get away a bit more from the "big/small guy" game mentality there, at least that's what I think... I like to take a more holistic approach there.
Off the mat, key focus areas are flexibility/mobility/fluidity, aerobic cardiovascular base, and explosive/dynamic anaerobic work. I find that that combination, when kept on top of as part of an overall fitness regimen, helps me best utilize the natural attributes of my size and strength, while making up for or correcting some of the weaker areas in my natural attributes.
I don't know if any of this will help you or not, but I hope something in there does.
Oss.
