How can I allow access to both SSH and SFTP?

You don't need to make any changes to the default installation of ssh to be able to use both sftp and ssh. All sftp is, is a means of doing file transfer over ssh.

This setting

Match Group sftpusers
...
ForceCommand internal-sftp

restricts access to sftp for the users in the group sftpusers. Either remove your user from the sftpusers group or remove that forcecommand option.