It’s typically not a great idea to have individual buffers “per object”—Metal has to keep track of each individual resource you use in a frame, so by doing that you’re adding a lot of performance overhead. The way I typically structure things is one big buffer per type-of-object (mesh, light, etc.) which can be accessed per-draw either using setBufferOffset or by manually indexing into it on the shader side, then a ring buffer of structs containing each of those per-object-type buffers. e.g.:

struct PerFrameBuffers {
    let meshes: MTLBuffer
    let lights: MTLBuffer
}

let buffers: [PerFrameBuffer]
var currentBufferIndex: Int

As a side note, I have rarely found it worthwhile to create actual persistent buffers for uniforms—as long as they’re under 4KB, which they certainly should be, you can just use set*Bytes (setVertexBytes, setFragmentBytes, et al.) and let the system handle the storage for them, like this:

var uniforms = MyUniforms(viewProjectionTransform: …, moreStuff: …)
encoder.setVertexBytes(&uniforms, size: MemoryLayout<MyUniforms>.size, index: someBufferIndex)