My brother had no clinical experience and ~50 hours of shadowing (all done during the month before he submitted his AMCAS - definitely looked like checklist-ing), and he's at Duke now for MSTP 🙂 The lack of clinical experience is okay for MD/PhD. While the lack of shadowing is not ideal, there's not much you can do about it now anyway (unless you want to shadow while abroad, which might not be easy/ might give you a different perspective than shadowing in the US). Checklisting is better than nothing, although I don't know by how much.
From what I've heard, most people who get interviewed are going to have pretty similar numbers, and at that point, matching your research interests with the school's matters more.
(also MSTP interviewees get treated REALLY well compared to regular MD interviewees...not very relevant but just a random observation haha)