> My guess is that the API, being higher level than vk/dx Metal is not generally higher level than VK/D3D12, instead it's a mix of high- and low-level feature

> My guess is that the API, being higher level than vk/dx Metal is not generally higher level than VK/D3D12, instead it's a mix of high- and low-level features (where the low level features typically had been added in later Metal versions and are optional to use). You can stick to the convenient high level parts of Metal v1 (which feels a lot like the spiritual successor to D3D11) if that's good enough (which often is), but if needed there are lower level and more explicit features that match or in some parts go beyond what Vulkan and D3D12 have to offer (AFAIK argument buffers allow a couple of things that are not possible on D3D12 or Vulkan, or at least would require vendor specific extensions on Vulkan - like setting the PSO via an argument buffer, recorded in a compute shader).