Hi Logan,
This thread is specifically about line graphics getting dropped in the exported file. I see that you are having a separate issue with legends. I can answer a few questions - however, I think if you want a back and forth a new legend-specific thread should be created.
A new legend fitting type was added at 2.7 - Manual Columns. This type was added because we found that the the legend item option "New Column" created a number of difficult issues with a few of the Legend fitting strategies. Whenever we make changes to the legend we work hard to not change existing legends. Unfortunately, our test suite is but a sample of the vast number of possible legend combinations.
It is possible that your "enlarged" legend is a bug. Not knowing the details of your legend (layers, size, properties, etc...) I can only guess.
You are welcome to log an issue with support. They are better equipped to handle troubleshooting steps and gather bug data. They can be contacted at https://support.esri.com/en/contact-tech-support.
Please refer to https://pro.arcgis.com/en/pro-app/latest/help/layouts/layout-fitting-strategies.htm for more information.
Thanks,
Tom