Ideal way is to get fixed retainers and use clear ones for night time wear . This should be  done for 6 months and then the fixed can ve removed and night time clear retainer wear can be continued. This helps to not only keep the teeth where they are after the treatment but also protect teeth from wear and tear due to grinding.

Upper transparent lower fixed ones. In few cases upper both fixed and transparent required

It is always better to put fixed retainers, as whatever we want achieve, we can get in fixed. Reason:--- they are very comfortable to wear ----- you can not control or wear off as and when you want to, so chances of misplace are less , you will not lose them while eating. ----- it is behind the tooth, so barely visible to others

Dear practo user Any retainers function is to retain the teeth in position and preventing relapse, and strengthen bone from inside. Whichever system you choose or follow, ultimately goal is the same. It's always better to follow your orthodontist suggestion as you are unsure.