No, TIFF is not compressed unless you request it compressed. DNG is an open architecture file format where as NEF is a proprietary format. But the more I read your questions, the more I see you're interested in the nuts and bolts of digital images. So I'll provide a bit more information. Understanding the formats is only the tip of the iceberg, there is also the issue of color space. You can request your camera and software to utilize sRGB or AdobeRGB or even ProPhotoRGB, all of which can affect the way your image looks. On top of that there is also the issue of your monitor and exactly how it deals with these various color spaces. This bridges directly into the calibrating your monitor. Chances are the image you're seeing on your monitor is not the same as what I'm seeing on my monitor and more importantly, it may not be the same colors you'll see when you print out your image. What many people do in this case is to calibrate their monitors to match the proper color space they're using.
But I digress... what I would suggest at this point is to put these issues on the back burner and instead focus your energy on learning your camera inside out and to being understanding the variables of photography - aperture, shutter speed, depth of field, as well as techniques like panning, avoiding lens flare and diffraction, maximizing bokeh, utilizing the golden hour and reducing hand held camera shake. And once you have a handle on these items you can being studying photographic composition, the rule of thirds, the golden rectangle, color theory, gestalt, etc.
This is why I love the art of photography, there's plenty of room to swim in the deep end.