20 attributes is absolutely no problem. There are ~500 system attributes already; 20 more won’t be noticeable.
10K notes is getting up there. I don’t think this is technically prohibitive, but you might want to think about organization a bit. A list of 10,000 titles is not very useful; a map view with 10,000 items is too big to see. So, you’ll want to use containers, or possibly separate documents, to get a handle on your notes.
What sort of notes are these?