It's also possible to say "nothing" and just leave it at that. A lot of people are desperate to defend Apple by looking at security from a relative perspective, but today's threats are so widespread that arguably Apple is both accomplice and adversary to many of them. Additionally, their security stance relies on publishing Whitepapers that have never been independently verified to my knowledge, and perpetuating a lack of software transparency on every platform they manage. Apple has also attempted to sue security researchers for enabling novel investigation of iOS and iPadOS, something Google is radically comfortable with on Android.
The fact that Apple refuses to let users bring their own keys, choose their disc encryption, and verify that they are secure makes their platforms no more "safe" than Bitlocker, in a relative sense.
I don't think this is precise, but the constraints seem a bit vague to me. What do you consider to be in the list of secure devices?