Ok, my experience with various monitors in your size range (and tegus).
Savs - Tend to tame down but cannot be guaranteed, 99.99% are wild-caught (I've never even heard of captive bred ones), VERY prone to obesity (even moreso than most monitors), can get surprisingly large (5'6" is the biggest I've seen), need to be able to burrow.
Dumerils - More commonly CB than Savs, but much less common in the market, tend to become an unattractive dark brown when adults, require more vertical space than a sav, much less hefty and less prone to obesity. Usually quite tame.
Mangroves - Imagine a Dumerils on meth. Nervous, flightly, VERY fast, but not terribly prone to biting. A good display animal, but won't tolerate handling well, and needs a tall cage with lots of branches. I don't know of any CB individuals, but there may be a few dedicated breeders.
Timor monitors - like a more terrestrial mangrove, basically. Still nervous and flighty, though.
Argus/Gould's monitors - VERY smart, which can be good or bad. Hard to predict if they'll tame down.
Blue or Green tree monitors - $1000 of "OH GOD IT'S BITING MY EYES!!"
Ackies (varanus acanthurus) - actually an excellent choice for your situation, small, energetic, interesting, can be kept in groups, can be fed roaches throughout life, and they hold value well in case you want to sell them later. Check Pro Exotics for lots more info.
Now, on to tegus. Species primarily determines disposition.
Gold tegu - The lovely gold-and-black pattern stands out lovely when contrasted with your blood. Untamable. Avoid.
Columbian B&W tegu - NOT the same thing as the argentine - smaller, darker, and a whole lot nastier. Not as bad as the Gold, but less than 1% tame. Invariably WC.
Argentine B&W tegu - will become puppy-dog tame. Will also exceed 5 feet long and 15 lbs. They eat a mix of veggies and meat, probably about 50:50, with adults eating more veggies and babies more bugs. Still, adults will love roaches. Almost all CB. "Chacoan" or "white-headed" tegus are just a variant of this species from a different region.
Red tegus - Even bigger and slower than Argentines, can top 24 lbs. Mostly herbivorous. Almost all CB.
Blue tegus - harder to find and more expensive, by my favorite (I have one). They feed entirely on meat, are smaller than most other species (my big male is only a few inches over 4 feet), and are easy to tame (though they're more active, preferring to roam rather than sit and be held).
Mokele
