I went to an RC convent from 5 to 18. In my class it was fairly equally divided between RC (which I am) and not RC (mainly they would have been C of E in those days - I am a proper old gimmer educated in the late 70s/80s).
I came out of school with no feeling that I was in any way inferior to a boy or man - quite the opposite - but it was an all-girls school, and I think this probably makes all the difference in any school really. We were encouraged as much to aim for science as for the arts and I genuinely never felt that because I was a girl I should go for one type of career over another.
As for Religion, there was a lot of it definitely. We even had retreats where priests would come in for a week at a time and give masses each day and hold special sessions with each of our classes. But that was actually quite fun and as we only had female teachers otherwise, was an interesting distraction for us. From recollection, non-RC pupils attended all these too, and the Masses, but just didn't take Communion.
Regardless of your religion or lack of it, R.E. O' level (I said I was old) was compulsory, and they made us do the dull syllabus where you had to learn the Gospels by rote rather than the interesting one about world religions I discovered when I read the paper. Again, that might have changed or may have been more down to the nuns' choice. I suspect a compulsory RE GCSE may still be a requirement though so, again, you might want to check that and whether there is some flexibility over syllabus.
Also, the abortion thing - I don't know if it is still common in RC schools but we had to sit through an incredibly grim film on the topic and we were put in no doubt at all that abortion was wrong. I am not aware that anyone was scarrred long term by the film or that it changed people's minds one way or the other really, but it is definitely something to bear in mind and find out what the policy is.
I don't think I would worry about your DDs being taught too many religious stories. They will be, of course, but they also live with you and in the real world and should get a balanced view overall. You don't get taught Creationism in Science classes in an RC school, for example, (or at least we didn't). I was completely unaware at school that some Christians still genuinely believe that the world was created 5000 years ago or whenever. I assumed everyone regarded the Bible, or at least the Old Testament, as part history, part stories passed down to explain things people didn't understand back then.
Sex education may be the biggest issue. I am not sure how that will be approached and you might want to check that with the school. We had none, apart from the bare science aspect, but that may have changed.