Will new DB objects be created in old custom tablespaces if not migrate to OATM ?

Hi,

Currently, we have created custom objects under own tablespaces. We see that it is optional to migrate all custom objects to OATM model during upgrade to 1EBS 12.2 and before enable online patching. We would like to know if there is any impact especial performance area of not migrating to OATM model? Also, when we create new DB objects under that custom schema, will the new DB objects be created in new OATM tablespaces or will still be created under the original tablespaces? That means will DB objects under the same schema but have using different tablespaces?

We are still puzzling whether we must go through the OATM migration process, as we are afraid that the OATM migration process will take a very long time but we only have a very short period of system down time for upgrade. Would anyone please advise? Thank you so much!