My understanding has always been that a trust document's provisions can't override the IRC. Reg 1.265-1 requires a reasonable allocation of expenses to tax-exempt income. There are various methods that could be considered reasonable, but a zero allocation wouldn't appear to be reasonable on its face.

The powers you cited - 1. appears gives the power to choose on a decedent's estate/trust whether to deduct a given deduction on the 1041 or the 706. 2. appears to give the power to decide the timing of a deduction or income, but my understanding has been, that type of provision usually applies to the trustee's determination of amount of fiduciary accounting income that is distributable to a beneficiary, not to taxable income.