If you want a backup plan for peace of mind, bear in mind that the space under the seat in front of you (presuming no bulkhead) is 100% yours. Bring a packable single use bag (<$10 on Amazon) and, if it becomes a problem, toss your meds and the valuables in that bag, carry it on and gate check the larger item.

Do bear in mind that this really is simply a peace of mind exercise.