How many legacies

I don’t think any chapters take all legacies. That would be almost impossible. The only legacies that really get in are ones that are on the actives radar. For example, say there is a girl who is a legacy and she lives in another state. She has no friends in the house and she hasn’t made any effort to make connections. This girl might not be on that house’s radar. Some chapter prioritize getting in-house sisters because if she ends up at another house, then it looks like they “stole” her. To make a long explanation short, no, legacy status is not that important but it might give you an edge if you put yourself out there

Some chapters have over a hundred legacies come through and there is no way they could or would take all of them. So now they have legacy limits. It's one of the reasons there was a huge shift a few years ago to eliminate preferential treatment for legacies.
Honestly, unless a pnm has a in house active sitting sister while she is going through recruitment, there are no guarantees. Plenty of triple legacies get cut so leave all your options open.

Most sororities have eliminated required special courtesies for legacies; pnm's have to get in on their own merit. This has been a great thing for the sororities because now they don't have to cut girls after 1st round to make spots for legacies that they really aren't interested in. Nobody really cares about legacies from other chapters anyway, it only matters if you are a legacy from the MS chapter and then only if your legacy relative has some current connection to the chapter as an alum.
Nevertheless, legacies should always let their legacy house know they are going through rush and get a rec because you never know how any little thing will help.