Ryzen hasn't really supported overclocking for a few generations. PBO provides the best results.
It's worth noting that while PBO is an important part of being able to get the most out of a Zen 2/3 CPU (particularly with curve optimizer tweaking), AMD
also officially considers PBO overclocking. As such it's likely that neither manual overclocking or PBO will be supported with this 5800X3D SKU. It'll almost certainly be locked to the default 142W PPT, with 95A TDC and 140A EDC values.
Adjusting global voltage (such as an offset undervolt) may still be possible, but results from doing so are typically very small as you're limited by the stability of the weakest core. In this case, it could potentially be held back by the additional 3D cache TSVs as well.
Robert did mention maintaining FCLK and memory tweaking (which, along with voltage offsets, tend to be "front page" adjustments, and not found in the AMD Overclocking submenu), which is good. Hopefully the addition of the 3D cache does not make FCLK adjustments more sensitive - if it does, the normal ~1866-1900MHz sweet spot may see a reduction. Ditto for the IMC still being capable of solid 3600-3800MT performance, as on the normal SKUs.
Fingers crossed.
My
hope is that at some point soon after launch, whether intentionally or otherwise, it becomes possible to make these manual adjustments - even if it isn't in the best interest of most people as far as any potential performance improvements go. Perhaps leave them accessible through tuning software, rather than at the BIOS level.
Simply having the ability to explore the architectural relationships between voltage planes, frequencies and thermal/power management should lead to a better understanding of their stacked 3D cache design, pinpoint strengths and weaknesses, edge cases and ultimately allow for better feedback when it comes to potential future high performance products. The enthusiast community can be a right pain in the ***, but it's also effectively a large scale volunteer QA team. Take advantage of it.