Non-citizens who own assets in the United States can plan their estates through various methods. Here are some of the common ways non-citizens plan their estates in the United States:

1. Create a Will: Non-citizens can create a will to distribute their assets to their heirs or beneficiaries. A will can specify who will receive the assets and in what proportion. It is important to ensure that the will complies with the laws of the state where the assets are located.
2. Trusts: Non-citizens can create a trust to hold their assets. A trust can be revocable or irrevocable, and it can be set up during the lifetime of the grantor or created in a will. Trusts can provide asset protection, minimize tax liabilities, and ensure the assets are distributed according to the grantor's wishes.
3. Joint Ownership: Non-citizens can hold assets jointly with a U.S. citizen or another non-citizen. Joint ownership can provide some protection against estate taxes and simplify the transfer of assets upon the death of one of the joint owners.
4. Gift-giving: Non-citizens can give away their assets as gifts during their lifetime. However, there may be gift tax implications depending on the amount of the gift.
5. Use of Trusts: Non-US citizens can use trusts to hold their assets in the United States. A properly structured trust can provide asset protection, minimize tax liabilities, and ensure that the assets are distributed according to the grantor's wishes.
6. Use of Entities: Non-US citizens can use entities such as limited liability companies (LLCs) and corporations to hold their US-based assets. These entities can provide asset protection and can also be used for tax planning purposes.
7. Charitable Giving: Non-US citizens can make charitable gifts to US-based charities. Charitable gifts can provide income tax deductions and can also reduce the value of the estate, thereby minimizing estate tax liability.
8. Marital Deduction: Non-US citizens who are married to US citizens can use the marital deduction to minimize estate tax liability. The marital deduction allows for unlimited transfers of assets between spouses without incurring estate tax.

It is also important to do planning prior to seeking US residency or citizenship since those classifications require that your worldwide income shall be susceptible to US tax as well as other US based taxes like gift and estate.

Generally, a drop-off trust involves transferring assets into an irrevocable trust structure where the grantor relinquishes control and ownership over the assets. By doing so, the assets may be removed from the grantor's taxable estate, potentially providing estate tax benefits in the future.

For a non-citizen alien seeking a U.S. residency visa, utilizing a drop-off trust might have certain implications and considerations:

1. Residency Status: The specific residency status you hold or plan to obtain can impact the taxation of trust income and assets. Different tax rules apply to U.S. residents, non-resident aliens, and resident aliens for tax purposes. It is important to understand how your chosen residency status affects your tax obligations.

2. Estate and Gift Taxes: The transfer of assets into a drop-off trust may have implications for U.S. estate and gift taxes. While U.S. citizens and residents are generally subject to U.S. estate and gift taxes on worldwide assets, non-resident aliens are generally subject to U.S. estate and gift taxes only on assets situated within the United States.

3. Reporting and Compliance: The establishment and ongoing administration of a drop-off trust involve complex reporting and compliance requirements. Non-compliance with these requirements can lead to penalties and other legal consequences. Consulting with a qualified attorney who can guide you through the process is crucial.

it is equally  important to note that the laws governing estate planning for non-US citizens can be complex, and it is advisable to seek the guidance of an experienced estate planning attorney who can provide advice tailored to the individual's specific circumstances. As well as put an astute tax preparer on the team to ensure compliance is in accord with laws.