Travertine patio

I am a first-time tile-layer and preparing to lay 6x6 tumbled unfilled travertine tiles on my outdoor concrete patio and I had several questions concerning grouting and sealing that I was hoping someone could help me out with:

1. What is the optimal grout joint size?

I've seen many people recommend 1/16" on this forum, but I was thinking about using 1/8-3/16" joint because I was told that I needed to use sanded grout. I figured 1/16" would be too small for use with sanded grout.

2. When/Should I use sealant/impregnator/grout release and what kind do you recommend? Should it be used before/after grouting, or both?

There seems to be quite a lot of disagreement concerning this issue on the various online forums. I had planned on grouting over the holes on the surface since this will be outdoors to keep water, dirt, and debris out of the holes. Some recommend using these products before grouting, but it seems to me that the grout would not adhere as well if applied after the sealant/impregnator product and there would also be a risk of the sealant product draining into the joints and affecting the grout adherence there as well. I do plan to use a sealer after the grouting is completed.

3. Is sanded grout appropriate here or should I consider smaller joints and unsanded grout?

4. Can grout be color-matched to my specific tile, or should I just pick the closest color I can find in the store to the palette of colors in my tile?

Thanks in advance for your thoughts and advice!!