Setting up some mavic crossride wheels tubeless later what size tape do I need.

From personal experience with XM719’s (same rim) I would recommend using stans standard rim strips rather than just tape as the tyres are a loose fit on the bead benches and you will struggle to get them inflated. If you want to have a go with just tape then you want some 21mm wide stuff as the rims are 19mm wide and you’ll lose a bit of width as it follows the profile of the rim.