Some sensors have global shutter instead, which makes it even more like DRAM: Conceptually each pixel has a capacitor and a photodiode, and a transistor connecting the two, all of these transistors are connected in parallel and form the "global shutter signal".
Some sensors have faster ADCs and use one ADC for a bunch of columns, which has been claimed as the source of column-banding in some sensors (unclear if correct).
[1] Sensors that are intended for both photo and video typically support things like pixel binning, where the sensor itself averages e.g. 2x2 blocks of pixels internally. A lower quality alternative is line skipping, where the sensor is told to only read out every nth line, thus reducing resolution considerably. The higher quality alternative is "full-sensor readout", i.e. the camera reads all pixels and downsamples the image to the video resolution. I believe some (announced?) sensors can do this in the sensor itself now.
Note: A lot of this is "somewhat informed speculation" on my part, because image sensor manufacturers tend to be very secretive of their sensor's details.
A library like libraw reads most RAW files and can give you an appropiately (for the sensor used) debayered RGB image. These images aren't in a defined color space; they're specific to every camera/sensor.
In the moving pictures space OpenEXR is a common format for "arbitrary" images, since it allows any number of channels each with different formats (e.g. you can have a file with 27 channels per pixel, some of which are float and some of which are integer).
[1] E.g. 12 bit log encoding gives even resolution across more of the dynamic range; a linear encoding gives half of each range to the brighter stop.
[2] Sensors that don't have PGAs simply have a fixed sensitivity. If the camera offers an ISO setting, it is emulated in the digital domain by pulling the image.