All the Bastille floors I've done , I have used Mapei Ultra colour grout.
It's s nice coarser grout than most and most importantly for me , rapid setting. Which helps keep a nice flush joint.
And comes in loads!! Of colours.
As for the expansion strip if one is required , then either to suit tile colour or grout , not many options as you say when you need deep ones.
You could make your own cold joint if you get get suitable metal flat trims of that depth and then use Mapeis matching Silicon to the grout , setting a min 10mm cold joint.
It's s nice coarser grout than most and most importantly for me , rapid setting. Which helps keep a nice flush joint.
And comes in loads!! Of colours.
As for the expansion strip if one is required , then either to suit tile colour or grout , not many options as you say when you need deep ones.
You could make your own cold joint if you get get suitable metal flat trims of that depth and then use Mapeis matching Silicon to the grout , setting a min 10mm cold joint.