Please help me in understanding the below issue :

SQL Server Version 2014 with AOAGs. We have separate Data , Log , temp DB , SQLFS Drives individually.

Our Backup Strategy is as below:

* Weekly Full Backup
* Daily Differential
* Every 15 Minutes Log backup

My Total Log drive space is 300 GB.
When I checked the DBCC SQLPERF(LOGSPACE) only tempdb is highest consumer.

AutoGrowth Settings :

[![enter image description here](https://i.stack.imgur.com/h8eiY.png)](https://i.stack.imgur.com/h8eiY.png)

**NOTE :** Currently I have only 20% free space left. Autogrowth is in '%'.

Also we have Filestream data enabled . Will Filestream have separate Log file ?

Result of T-Log utilization:

[![enter image description here](https://i.stack.imgur.com/aXRJ4.png)](https://i.stack.imgur.com/aXRJ4.png)

Please help me with below concerns as I am new to SQL Server DBA.

1. In what case I should go for increasing my Log drive space . For ex: E:\ is for my SQLLOG, in what case I should expand or increase my drive. What is the end point I should consider before expanding drive ?
2. Sometimes DBCC Shrink does not free up much space ! what could be the valid reason.
3. And I read some articles where it is mentioned not to use Autogrowth in '%' instead we should use in 'MB's'. I have mentioned my case above . Kindly correct me if I am in good lines or false affect. Please correct me and help me on going for good considerations.

Thanks