What is the policy for warranty of Mikrotik devices bought from Amazon?
Ask Amazon or read rules which you accepted during purchase.
Is it best to purchase Mikrotik devices from the Mikrotik Official Distributors list?
Depends on the warranty conditions they provide.
Compare and see what works best for you.
Also take into account potential returns and how you need to handle those.
The main advantage of Amazon purchases is fast/free delivery, and their 30 days return window on almost everything. You’re basically at the mercy of the third party vendor or the manufacturer thereafter, at least according to Amazon.
I am lucky to be protected by very strong consumer laws, but I have had to threaten them of filing a complaint/closing my accounts on more than one occasion to get help on defective items. In every case, they just issued a refund or asked the third party to handle the RMA.
Honestly, when not purchased directly from Amazon (sold by), it’s not worth the possible hassle unless it’s an authorized dealer. YMMV.