The first is a new ruler. Present in the draw tab of the ribbon, it lets users draw straight lines or align sets of objects. You can pivot it to any angle from horizontal to vertical with a degree setting for precision.
The second is changes to PowerPoint's hyperlinks. Users were previously able to create them by pressing enter after a link and editing the text. They can now select the link after and change the font color in the home tab of the ribbon. This will be essential if the text is on a blue background.
As mentioned, you have to be in the Office 365 Insider program to get access to these features. You'll be trading stability for more frequent updates, so it's worth considering carefully. These additions will eventually come to regular users in June, alongside a multitude of others across Word, Excel, and more.
May 2018 Update for PowerPoint
The features join those from the May 2018 update, which released on the 14th. PowerPoint got the ability to restore earlier versions of files saved to SharePoint or OneDrive. Outlook for iOS got support organization hierarchies and a faster file preview.
In April, PowerPoint's Inking got an upgrade, letting users take notes using a pen and convert them into readable text and shapes.
Unfortunately, those not in the Office Insider program for iOS won't be able to get the June 2018 update. Microsoft isn't accepting applications but encourages users to check back soon.