Will the new tax bill affect flow through entities' / S Corps' 2017 tax rates? Specifically, will you be able to take advantage of the new 20% deduction for 2017?
Section 11011 of H.R. 1 (pages 10-18) lays out the 20 percent deduction for pass through entities. Subsection (e) reads:
(e) EFFECTIVE DATE.—The amendments made by this section shall apply to taxable years beginning after December 31, 2017.
That is, the 20% deduction does not apply to the return you are filing for 2017.
Your first question, "how will the new tax bill affect tax rates," is far too general and situation-specific to answer in any useful way, unfortunately.