All calibration images should be taken at the same size/resolution/bin level.
Darks - Same exposure, gain, and temperature as the lights. Use a 50/50 Red/Blue setting with OSC cameras to maintain a baseline color balance.
The purpose of Darks is to remove camera noise, including Amp Glow, Thermal Noise, and Hot/Cold pixels. This is all about the camera electronics (not about the image/optics/light). EAA generally uses short exposures, so Darks will have very little impact, however, you can create darks for your common settings and use them over and over, known as a Dark Library. This is much easier if you are using a cooled camera. Without a cooled camera, you may want to take Darks just before or after your Lights, in order to match the temperature.
Flats - Same brightness as Lights, monochrome, bias, 50% luminance on histogram. Use the gain setting that produces the least noise (know your camera, it might be 0, it might be 120, or 350, depends on camera)(exposures can be very small if using a light panel, milliseconds, just shoot for 50% luminance).
The purpose of Flats is to remove light gradients, vignetting, dust motes, etc. This is all about the image/optics/light. The orientation of every piece of glass in your imaging train needs to be the same as your Lights, including focus. Don't fret about the very fine/minute focus you might make because of temperature changes or seeing conditions, but take your flats at the same "infinity focus" as your Lights.
“Brightness” is also called “Black Level”, and sometimes “Offset”. If you use the Sharpcap Smart Histogram Brain Window, it can measure your sky brightness and tell you the Optimal Black Level. For me this is 4. It will even automatically set the Brightness slider for you. Take your Flats and Lights using the same Brightness. Flats will make a great impact on your EAA imaging, I highly recommend them. You will need to figure out when the best time in your workflow is to take Flats, this will depend on what method you use (t-shirt, twilight, flat panel, etc). Personally, I use a cheap light panel which is simple and fast. I take Flats "on-the-fly" just before I start imaging Lights. Generally, you do not reuse Flats from night to night, although they can be used on all targets in a single session as long as you don't rotate any glass in your imaging train. Theoretically you might reuse them, but in practice something always changes... the scope is jiggle in transport, a dust speck falls on your lens, etc. Learning to take Flats "on-the-fly" with a light panel makes this calibration frame fast and easy, so much so that you can rotate your camera to frame your target "just so" and quickly take new flats just for that target.
There are many threads about calibrations frames, methods, and equipment for such. I can also be more detailed here if needed.