There is no matching of days off function in bidding. FOs do tend to get more days off than Capts so could work out, sometimes .
If one of you takes the company accommodation, the other does not get paid the allowance. If you both opt out of company accommodation you both get the allowance.
You only get the annual leave travel from one of you, so pick the one with better upgrade potential.
Getting leave periods together can be challenging. Even off peak.
Lifestyle will depend on which fleet you join. And that changes with time too.