Always sRGB. https://www.damiensymonds.net/2014/06/the-wide-gamut-myth.html
8-bit is fine in almost all cases. There are really only two exceptions:
Photos with very smooth areas (eg seamless backdrops or broad blue cloudless skies) that present a banding risk in 8-bit;
Photos that need more than the usual amount of Photoshop editing (eg severely hazy backlit photos).