I recommend you read this article (Managed vs External tables) and answer the following questions:
- do I require direct access to the data outside of Azure Databricks clusters or Databricks SQL warehouses?
- If yes, then External is your only option
In relation to the other questions take a look at this article (Managed Storage Location). You can you use more than one ADLS location, if for instance you have 3 catalogs (dev_bronze, dev_silver, dev_gold) and map each one of these catalogs with its representing ADLS location (adls-bronze, adls-silver, adls-gold). In your case it might make more sense to keep your existing ADLS and have three containers (Bronze, Silver, Gold or equivalent if using medallion architecture) and map each container to either a catalog or schema.
In terms of managed data lifecycle it gets a bit more complex. Read more here (in preview): (Archive Delta). Depending on the volume of data I would consider omitting this. Storage is cheap these days.