I have the impression that these things vary hugely from one catholic school to another.
Not always easy to find out beforehand though. Can you speak to any parents who have children at the school already?
My DC go to a catholic primary. Though only a small minority of the teachers are catholic, the whole school life feels VERY catholic. I'm non-catholic Christian (reformed/protestant) and find it weird that at every parents info meeting they start with a prayer, and if you don't make the sign of the cross you stand out. They also 2x/day call upon Saints to 'pray for us' which is something I'd never do. In the month of May (I think) the children are asked to have a rosary at school every day and they pray the rosary regularly. Of course children don't have to join in with these activities - the non-christian children at the school just sit quietly during the four daily prayers. But those children who e.g. memorise the Hail Mary first get extra praise, those children who volunteer to be prayer lead get commendation from the head teacher, the religious aspects are such a big part of the school life that those children who aren't Christian, and to some extent also those who are non-catholic Christian, can never really be a fully included member of the school community. Which I think is a shame.
But that is our school. It needn't be that way and especially in an undersubscribed school, where you'd expect a fair number of non-catholic children, I would think that they would handle things better.
If you have further children, check the admissions policy with regards to siblings. If this school really is good (your feeling says it is), it might suddenly become very popular, oversubscribed, and your younger child might not get a place - if they prioritise catholics over non-catholic siblings.