Phase 4: Clean up other APIs

[aleksa-krolls]

See parent issue #887 for details.

[martalovescoffee]

@hunterachieng could you please add an estimate to this issue?

[josephjclark]

This will be a breaking release, so we should take a breath and make any other breaks we want.

For example, we should remove callbacks here (the API is inconsistent right now)

[josephjclark]

Consider phase 6: any changes we want to make for the sake of documentation, we need to do here.

i suggest:

1. we remove the other APIs
2. before we release, review what's left and tweak signatures