The preferred method is creating a temp or maint pool. Then select Member2 and move it to that pool. This will leave all the data StoragePool 1. Once it's in completed and in the "maint" pool, you can select Member2 and use "Delete Member" option to remove it from the group. This will properly remove it from the group Database and reset it back to factory default. Then you can add it into the new group and reconfigure it.
This assumes that Member1 has enough space to hold all the data that is in Member2. Otherwise you will have to backup the data, or move it to other members in the group to free up enough space.
In the case of the single member pools, you will need to backup or replicate that data somewhere then delete the volumes on those members. Then you can delete them from the group.
Once you are down to the last member and the data is gone, you can use "reset" at the Group CLI to return that member to defaults. NEVER run reset on a multiple member group!! Only on a single member group. Even if the member is in its own pool, NEVER EVER run 'reset'