If I have a 1TB volume with a 900GB Lun both thinly provisioned – 200GBs worth of data which is consuming 200GBs from the aggregate do I need volume autogrow enabled to allow the volume to grow up to 1TB (assuming there is sufficient free space in the aggragte)?
If "vol size <volume>" really says 1TB and "lun show -v" really shows LUN size 900GB, then you dont need autogrow unless you are using snapshots. If using snapshots you should set the autogrow to ~2.3 times of the LUN size.
