Advanced Settings are available on all platforms except Android. The majority of the advanced settings should be set on the Parsec Client, as the client defines the settings that will be used during the stream. The only settings that are determined by the host are in this section.
The advanced settings are available through configuration files on both the server and the client. The configuration file is stored in the same directory as the software. There is a link in the Parsec Application to the advanced settings where you can add any of these settings to your configuration file. Before changing these, please try some of the more basic settings. Here's a helpful link to get you started optimizing your settings. All settings must be on their own line. Most settings are managed through the client except those listed in the server settings section of this document. You can access Advanced Settings directly in the app in the settings area.
Or you can find the config.txt file on Windows here (C:\Users\%username%\AppData\Roaming\Parsec\config.txt) or on macOS / Linux / Pi here (~/.parsec/config.txt)