Just to clarify the Spawn Larva mechanic that we're currently testing, it's just allowing players to queue up spawn larva. So for players who are hitting injects at the correct times, there's little change compared to HotS. It's not giving anyone any faster Larva per hatchery.
Also, for the macro mechanics, we're looking to fully explore and get feedback on this version. Like we've said, we're 50-50 split on what to do here at the moment, and the hope is to try various versions of the change in order to learn more about the whole situation so that we can make the right call.