Notability might be the best choice if you need write down a lot of details, for sketch and graph only, penultimate would be easier to use and faster.
You can set up dropbox on your mac and notability, it will automatically upload it in pdf foramt.
Beware, it claims it as autosync, but if you edit the pdf(A) on computers the edited version(B) won't be downloaded to ipad, and if you edit the original version(A) on ipad, it(C) will overwrite what you edited on computer(B).
Apart from notablity's functionality, it only costs you 0.99 dollar. All other usable ones cost you 2.99 at least.
Other noteworthy handwriting (some of them support typing too, BTW notablity does ) notetaking apps are, noetsplus, noteshelf and notetaker HD, a lot of people said upad is good as well but I tired the lite version and it sucks on new ipad.
If you only need typing, go with evernote then. Free of the best ones, best of the free ones.