The following settings are crucial to make the app work without any problems.

Set iRacing windowed and borderless mode. You can find it within the game under the graphics tab. Unselect the Full Screen and the Border boxes. (visually there will be no difference. Windowed borderless mode looks exaclty the same as fullscreen mode. Make sure you restart iRacing after this change. )

Set the Max Cars to 63 (this will not cause any performance impact, this settings is purely for how many drivers you get data from iracing)

In case you experimenting issues with standings and driver positions, make sure you set your network bandwidth in your iracing's account settings. You can find it on the iracing website under account page. Set Connection Type to 1Mbit/sec.

Connection Type

The Connection Type selection in My Account controls the maximum amount of data that the sim and the race server will exchange with each other. The higher the setting, the more data the two are allowed to exchange (the bigger the "packet"). The bigger the packet, the more space there is available to send car information to you, and so the more likely it is that the server will send you positions for more cars.

The server has the ability to send cars to you (their positions, as well as some other information) using different levels of detail. The different levels of detail require different numbers of bytes of information to be transmitted per car. Depending on the number of cars on track, the amount of space available in the "packet", and some other factors, the server will choose an appropriate mix of the level of detail it includes with each car it transmits to you. The higher your Connection Type selection, the more likely it is that the server will choose the higher detail level for more of the cars in the field.

The level of detail sent for any given car won't have any measurable impact on your CPU usage or your frame rate.

The extra overhead of handling the larger packets that can be generated when using the higher bandwidth selections might have a measurable increase in CPU usage IF there are enough cars in the session to actually use that extra space. See Max Cars below.