HTC Sync Manager will no longer be supported.
To transfer content from one phone to another, download the HTC Transfer Tool to your old phone and use it to transfer content to your new phone.
For details, see Transferring content from an Android phone.
Before you do a factory reset, back up your phone data to your Google Account which will be stored in your Google Drive storage. After the factory reset, you can restore your data while setting up your phone.
To transfer content between your Mac computer and HTC phone, you can use a file transfer software such as Android File Transfer on your computer. Go to android.com/filetransfer/ to download and learn how to use Android File Transfer.