You really don' need more than a megapixel of image in any case. Most monitors are set to 1024 x 768 pixels, which is pretty well a megapixel. Any hihger resolution setting just makes icons and text too small for use on Wndows with the average monitor size.
Higher resolutions are only useful for truly huge monitors (30 inch plus) and even then at normal viewing distances images don't need a lot more than a Megapixel, as you would not use the full screen area.
Also, the resolution of your camera lens may make higher resolutions immaterial in any case. It is quite common for cameras to have sensor resolutions much higher than the lens resolution. This helps reduce noise (graininess) in the image, and moire like fringing effects when image detail (Eg vertical stripes) clash with the pixel grid. If there are many more pixels than the lens can resolve the problem disappears.
So more pixels does not mean more detail, just better resolved blur!
In most cases a high or medium quality jpeg compression of a megapixel image will be less that 100k, and a megabyte is generous.
However exactly how well an image compresses depends on the image content, so you might find that one image will compress very small, and another might be almost the same size as the raw data!
In most cases however, the camera will do a good job, and it's a lot quicker than messing about with post processors.
The same applies to colour balance. Best done in the camera. (or better still using external colour balancing filters, but that's a bit advanced!) The reason is the same, time spent post processing to correct errors is better spent in other ways.
The color balance can be quite important. I hust got a neutral from a buyer who complained that the colour (Black) was exactly as described in the listing (ie black) and the title (Black!). Why he thought that the colour in the picture looked a bit brown!
(Which took some stretch of the imagination. I mean I used to have a job where I had to actuall asess the exact shade of black of a carbon sample. They were all as black as spades, but next to the reference black you could under a good light see quite a range of colour. I had real diffculty seeing brown! Of course there is no real black on monitors just the colour of the un-illuminated screed!)
I would not rely on the cameras 'auto' balaning however as this can get it dreadfully wrong! Three schemes are used to do this, one looks at the brightest part of the picture and decides that it must be white (Obvioulsy not true in many cases) another looks at the whole picture and adjusts the colour until he average colour is grey (Again you can see a problem there) the third looks for a parts of the picture which are nearest to 'white' (Grey) and adjusts the balance to get the average of those nearest to grey.
In all of the above schemes you notice that at no point does the camera know for sure what the actual colour is. So it is best to manually choose the best colour balance.
But be aware that your eyes can play tricks too, so to get an idea of the best settings for your photo-set take a series of test shots of typical subjects under the range of lighting you might have to cope with. (We don't all have deicated photo booths!) If you make a note of the settings you used each time you can display them on your monitor and decide which is best.
Don't forget that you really ought to set your monitor up too. You can dwonload tools to help you do this from various sources. It's not difficult.
These tools are not as good as the external colour measuring tools used by pro's to exactly calibrate their monitors, but you don't need that amount of prescision. Just a good average balance so your pictures will display reasonably accurately on other peoples monitors.