This article describes FTP settings that can improve upload and download speed.
Select burger menu > Global Settings > FTP tab in V9 (or newer) version (or Preferences > Options from the main menu and go to the FTP tab). See the help file for details.
Also, V8 introduced threaded scanning which can greatly reduce the time it takes to scan an FTP server. To use this, modify your profile, go to the FTP -> Advanced settings page and increase the Scan Threads value. See the help file for details and limitations.