Inherited Accounts

[TxInquirer]

Finally a great forum for tax info ! Here is my unique situation:
I am a retired Canadian citizen who always lived in Canada and never worked in United States. As a Non-Resident Alien, I have inherited a Roth IRA and Individual IRA accounts which were more than 5 years old from my sister who died on October 2022. So I applied on March 29, 2023 for an ITIN number and received it on August 16, 2023.
These Charles Schwab accounts were settled in my name on December 5, 2023. The long delay was because originally the accounts belong to Ameritrade and was acquired by Charles Schwab. There was also a long delay in obtaining the ITIN number. So they posted a 1042-S form on March of 8th for the Individual IRA account. The stated interest on this form is $4.00 @ 30% and my account summary on their website list a total dividend interest income of only $2.51. There is no form for the ROTH IRA account although the Charles Schwab summaries on their website in the account list a total dividend interest income of only $9.14. To date I have not withdrawn, transfer or deposited any funds from these accounts. So I sent an Election letter to Revenue Canada on December 12,2023. My understanding is that I am to withdraw all the money in both accounts over a period of 10 or less years. I will be starting to withdraw from these account this year in 2024.
My questions are:
1) Since the accounts were settled in my name in late December 2023, do you think I have to file a United States 2023 Tax Return now or can I wait for the 2024 Tax Return after I take out the yearly Minimum Required Distribution (RMD)?
2) If yes to the above, I understand that an interest total of over $10.00 should be reported, so what forms do I have to fill out? Do I file the 1040-NR form with a Schedule OI form? Should I also be filling out the 1099-INT form?
3) According to the US-Canada Tax Treaty the 30% dividend interest can be reduced to 15% since it would be considered periodic withdrawals? If so do I need to fill out the 8833 form or is this only for Resident Aliens or Expats?
4) Do I need to send an Election letter to the IRS?
5) Please confirm the specific Treaty Articles below that I should be entering in the Tax Returns.
United States = Treaty Article X (10) for the IRA 15% tax deduction?
and for Canada = Treaty Article XVIII (18) for the ROTH?

Any help would be greatly appreciated,
Thank-you.
Best Regards