Maybe. AFAIK, Premier can use as many cores as you have for export, and I export multi-hour long footage that takes easily 3 - 4 hours currently on my 3700X.
Whether I go NVL-S vs Zen6X3D depends entirely on what the benchmarks show. If they're within 5% of each other in gaming, but one is, say, 15% faster in Premier Exports, then I'll go with the later.
285K vs 9950X3D is
functionally tied in HEVC Encoding, but 9950X3D is much better in gaming, so if I were to purchase today, I'd go 9950X3D. But I'd just rather wait because both next gen is gonna see proportionally larger uplifts in this category than in gaming