Depends what you want to do, @bmxjeff. Modeling workflows tend to be bound by single-threaded performance due to floating point calculations. CAM workflows and toolpath generation tend to favor more cores.
Please note that our system requirements currently denote the minimum specifications needing to run Fusion. In general, I would recommend you get a processor with 6 or more cores and a base clockspeed of 3.5Ghz or better, and a mid-range or better dedicated GPU if you plan to use a 4k display. The performance level of a GPU is generally indicated by the second or third number in the model number, with a 6 or higher being performance offerings, and 5 or lower more entry level or low power - for example, 760, 2070, 6950, but not 550, 8400.
When it comes to Intel processors, newer ones have a concept of Performance vs Efficiency cores, with there generally being more of the latter than the former. Take note of the ratio of P to E cores for a given processor, as some models have, for example, 2 P cores and 6 E cores, instead of 8 cores of equal performance, and CAD software likes P cores. This does not apply to current AMD processor offerings. Additionally, unlike macOS we do not have native ARM support for Windows at this time, so I would avoid that architecture for mission-critical productivity work.
Lance Carocci
Fusion QA for UI Framework/Cloud Workflows, and fervent cat enthusiast