To do low key, it's not necessary to have a camera that will handle especially low light. High key feels light because the average luminosity is high. That doesn't mean the focus of the subject has more intense light on it. Just as it is in a low key photo where the average luminosity is low. And the perceived contrast is higher. It's not really higher. In fact, the actual reflective range may be higher in a high key photo. The lightest textured white (not dead white) is often exposed similarly in both low and high key. And the darkest textured area (not dead black) is also often similarly exposed in both. But high key lighting usually produces no featureless shadows. And low key usually produces no prominent featureless whites. (A photograph with significant areas of both dead white and dead black doesn't work. Snow has texture. Coal has texture.) You will see both high key and low key photos that take things very far, but the best photographs always use the full range of the material.
Now, don't think of high key as what you have been doing, although the typical three light setup is sort of lighting scheme also used in high key. In low key, often a single light source is used. But cut a small hole in a piece of paper and lay it over the cookies in the photo I posted. You'll see that the lighted areas of the cookies, like the one on the top left, are perfectly exposed and would have been perfectly exposed in any photo. You could set up the same scene high or low and use the same camera at the same settings. And the shadows in the shallow crevices of the cookies are very much as they would have been in any photo. You really can't tell by looking through that small hole at a part of one cookie whether the photo is high or low key. That doesn't become obvious until you see the deeper shadows and the black background. You might imagine that the low key version was the high key version but with the fill and background lights turned off. But that main light is the same as in the high key version, and the exposure is exactly the same for both. It's not the camera you're manipulating - it's the light.
Some think low key is more challenging. It's more challenging than classic lighting, but high key is just as challenging, if it's to be done right. And it's not that one subject demands one or the other key, but the interpretation you want for a subject will demand one or the other. Low key is dramatic, mysterious, and sometimes ominous. If you want to try some, start with lighter toned subjects. If you can imagine trying to handle chocolate brownies in low key, you see what I mean. It can be done, but it takes carefully chosen props and some very touchy lighting. A slice of fruit pie or a pizza might be a better place to begin.
What you may have trouble with is forcing your camera to properly expose in high key or low key situations. These are not over lit or under lit scenes, but an automatic camera will tend to see them like that and try to compensate, which will wreck the effort. If your camera will allow you manually set exposure or will allow you to lock in exposure, you can place an 18% grey card in the scene at the same place as the subject you want normally lit and note the exposure or lock in the exposure before removing the card.
If you use enough light that this exposure is within reasonable limits, close to about what you've been shooting, you will not have the noise that appears with long exposures in low light. If the exposure gets to long, use a stronger light. The great thing about digital is that you get to try lots of shots with lots of different lighting and different exposures. I learned about lighting and contrast using a 4x5 film camera. You think long and hard before you pull the trigger with big individual pieces of film.
"Kitchen duty is awarded only to those of manifest excellence..." - The Master, Dogen