Great question. Here's what the wiki tells us.
The QB decision for Week 1 is essentially Kirk Cousins. All signs point to him as the starter — Kubiak himself called it "his job to lose" after the preseason opener on August 14 (from the Kirk Cousins page). The organization has been explicit about not rushing rookie No. 1 overall pick Fernando Mendoza.
But there's an important distinction in how it affects Kubiak's play-calling:
If Cousins starts (which is expected): Minimal impact. Cousins has prior experience in the Kubiak/Janocko Shanahan system from his Minnesota years (from the Kirk Cousins page). Kubiak can call his full outside-zone, play-action playbook without holding anything back. It's essentially plug-and-play with a veteran who knows the language — you're getting the full Seattle-style scheme Day 1.
If Mendoza were to start (unlikely but not dead): Significant impact. Kubiak would almost certainly simplify — more run-heavy looks, condensed formations, heavy doses of play-action and Brock Bowers as a safety valve. The Raiders themselves have admitted the roster isn't "ready to support a rookie QB" yet (from the Raiders team page).
Bottom line: The Cousins decision enables Kubiak's full scheme rather than constraining it. The "waiting" headline from August 28 may just be procedural — the decision has been Cousins' to lose for weeks, and Kubiak's play-calling is built around that reality. If you're drafting Raiders skill players (Bowers, Jalen Nailor), the Cousins start is a positive for Week 1 efficiency.