How do the American superrich protect their money?

I can only respond to part of the question.

When a commercial property is purchased, the amount paid is not an expense, and so is not deductable from income for tax purposes. Depreciation is the allocation of the cost of an asset over its anticipated useful life. The useful life of commercial buildings are quite long, twenty-seven years is my best recollection. If that case, the owner can claim 1/27 of the cost of the asset every year as depreciation expense. Just for your information, you pretty much have to claim the depreciation expense because when you finally sell it, your capital gains tax is computed just as if you had taken it. Land, and the cost of land is never depreciated, by the way. Only the buildings and certain land improvements.

Gramatically, I don't know if 'depreciate' takes two objects. It seems to in the sentence, so it may be gramatically correct. So far as US accounting rules go, the sentence is dead wrong. Interest expense, whether mortage interest or any other kind is not depreciated over time. It is an expense in its own right, and is taken as a reduction of taxable income in the year in which it is incurred.

Watch out for the phrase 'creative accounting'. Sometimes, you have to be 'creative'. It should never be used to mean you are doing something illegal or dishonest. The usual term for that is 'cooking the books'.

I know very little about tax shelters, and nothing about trusts.

probably should be;

Landlords can depreciate / properties . . . and . . .deduct / expenses

That would be right.

Sometimes, it is hard to know if we are working with issues of language, or of fact.