You are correct. The Use Gmail activity in the Link-Gmail and Outlook package is used to send Gmail using POP3, while the Google-Workspace-Gmail-Trigger package contains a number of activities for sending Gmail using IMAP.
Which package you choose to use depends on your specific needs. If you need to send Gmail using POP3, then the Link-Gmail and Outlook package is a good option. If you need to send Gmail using IMAP, then the Google-Workspace-Gmail-Trigger package is a better choice.
Here are some additional resources that you may find helpful: