Can confirm, if the first chest placed is obstructed, the golem will not interact with the double chest. An efficient sorting system will heavily depend on this feature, but it has some workarounds, like allowing the copper golem to access both sides while restraining its movement with trap doors for example. As long as the chest is visible and at range of 1 block, the golem will search it.
That appears to be the case, yes. Having the golem place an unsorted item into an empty chest is also useful for sorting systems. The option to manually remove the item from the golem’s hands would be nice though.