You can select layers with batchPlay; see BatchPlay: Select layer doesn't work when multiple layers have the same name - #2 by jjdenhertog for an example.
You can see how selection works by using the Alchemist tool.
@Barkin Please include any additional information/examples you can. (Also, is this made any easier with api version 2?)
As for using the older CEP code and not being considered “legacy” – there is no provision for that.