Even I faced the similar situation a few months ago. I had a DPT (Default Policy Tag) set along with RPT tag that were incompatible with each other. In fact, you cannot have an RPT that performs the same thing as the DPT even if the time period is dissimilar. So, in my case, DPT used to move everything to the archive after 2 years. Then, RPT tag moved the Sent Items to the archive after every 3 months. These two tags were performing the same thing and Microsoft Exchange server does not allow it. As a matter of fact, if you attempt to create RPT tag after enabling the DPT, then Exchange Management Console will not allow you to do it. So, at the same time both were running together in my case, which resulted in the huge amount of transaction logs. But once we removed the Sent Items RPT Tag, right away the log generation stopped.
If both RPT and DPT are performing different actions, then there will be no problem.