Question regarding on how Apple rules propagate configuration/targets to `cc_library` or `objc_library`

[Winnaries]

With the release of @platforms, I can change targets of cc_library easily to arm64 by defining a set of constraints and using select() on those values. However, since Apple rules doesn't support @platforms and instead pass the config to C build configuration through --cpu and --crosstool_top. Being new to bazel, I am confused on how things operate over the boundary. Would be very helpful if someone can answer the following questions for me:

1. How does the Apple rules pass configuration to the underlying dependencies such as cc_library and objc_library? For example, if I want to build an XCFramework targeting x86_64 and arm64 that depends on cc_library target, how does the C target know which target to build and which toolchain to use under the absense of @platforms.
2. If I have a cc_library rule that uses select() on @platforms (eg. emiting TARGET_IOS local defines if the target is @platforms//os:ios) and have a apple_static_xcframework rules depends on it, what would be the result of the select? From my understanding, it would resolve to default condition, right? If that is the case, should I instead make select() on cpu for compatibility with Apple rules?
3. What would be the current best way to build Apple multi-arch library? Should I stick to using --cpu, or --platforms?
4. Lastly, will Apple rules adopt @platforms any time soon? I would be happy to help under some guidance.