If you like the look of the enhancer, that's all you need, yes, it's a sealer.
I would grout it all and fill the holes, that's the look.
Seal it before grouting, then if you wish, seal it all again and the grout a week later, but be carefull if using the enhancer if you seal it again, it can darken the stone even more, the grout too.
Normal sealer won't change the color, it might some, but 2 coats won't make a difference.