Can we implement Intended Use Feature without affecting Project Portfolio Management(PPM) tax rates?

Summary:

We currently use Project Portfolio Management (PPM) and interested to implement Intended Use Feature for our Creditable Withholding Taxes(CWT) in AR Module. However, we noticed that when we configure Configuration Owner Tax Options( COTO) from Standard Tax Classification Code (STCC)
to Determine Applicable Tax Regime (TAXREGIME), PPM tax determination is affected. PPM invoices no longer calculate tax automatically. PPM invoices are expected to compute tax based on specified rates on Customer Contracts. What could be the possible change in setup for PPM and Intended use to co-exist without affecting each other?