I recommend NOT using any color space other than sRGB, unless you really know what you're doing and have some specialty needs (like if you're printing in a high end published bound book, and know that when you're shooting and editing).
Changing between color spaces means that the edits you made may not look like you thought they looked (mainly the colors that are in one space but not the other must be changed somehow as a matter of definition), which is obviously bad. Even if the space you edit in completely contains the space you will publish in, that's still bad, because you'll THINK you can display certain colors, but will be wrong. Also, monitors can display sRGB pretty well, but not all of the range of many larger color spaces, so again, you're fumbling around blindly doing things that will probably not translate the way you think they will to the final product. sRGB is standardized and works everywhere, though, so you get exactly what you think you're getting. So again, unless you have specialty needs, use sRGB for no nasty surprises later on, because ANYTHING online, and ANY normal, low end print making services are all going to use sRGB.
However, when it comes to bit depth, you should always edit in the largest bit depth available, because there are zero downsides to that. Except possibly your computer running more slowly if you have a terrible computer. But other than that, no downsides. It prevents data loss and will not EVER cause you to be mistaken about how the final product will look, because your eye can barely even distinguish all the colors in 8 bit anyway, so even if you had a 16 bit capable monitor, you wouldn't be really seeing that much more in 16 bit. But it does do a LOT to protect your data from being lost across multiple edits.