First off, there's no need to worry about leaching tannins in the boil. Tannins are mostly found in the husk fraction of the malt. This means you have to be careful with the temperature only when the grain is in the water. So you should be safe in that regard.
However the question you're asking is what temperature to boil at.
'is there a temperature that is "too hot" to boil at? Is there a preferred range to boil in? Why/why not?!?'
Here's the issue: strictly speaking the only way to increase the temperature of your boil is to increase the pressure (by dropping in elevation, boiling in a pressurized vessel, or by increasing the hydrostatic pressure with a very tall vessel). Not really all that easy to do and unless you make drastic changes, you'll pretty much be boiling at the temperature dictated by your current elevation and equipment. Simply adding more heat doesn't increase the temperature (the heat that's being added while boiling is what's known as latent heat, and until all the water becomes steam, neither phase will exceed the boiling point at any given pressure).
What about the depth of your kettle? Well, it takes roughly two feet of water to make the bottom of the kettle experience a pressure increase of 1 PSI. This more-pressurized liquid would indeed experience higher temperatures during boil, roughly 215°F at 1 PSI over atmospheric pressure. I'm guessing most homebrew kettles are in or around this range of depth, and probably not many are more than a meter deep (which would put you at roughly 216°F at the bottom of the kettle). However, keep in mind that it's more accurate to measure the pressure at half the depth of the vessel, since that's the point at which half of the liquid will experience higher pressure (below) and half will experience lower pressure (above).
Concentration of the wort can be largely ignored; I did some math using this equation and found that at 20°P/SG ~1.080 the boiling temperature is elevated by less than 0.4°C/0.7°F.
That being said, if you can achieve a higher-temperature boil (by pressurizing it) you would see an increased rate of hop alpha acid isomerization (i.e. more bitterness) and higher rates of color formation (meaning your wort will get darker-er). Not much else is directly affected by the temperature though I know of many (not particularly relevant here) issues that go along with boiling under pressure.
In summary:
Don't worry about the tannins during boiling, only when grain is in the water. And unless you're willing to change elevation or equipment there's no real way to control the temperature of your boil anyway.
