Automatically start GTN750 in separate window on MSFS start?

[adminOwner2]

Yes, this is certainly possible by modifying an entry inside the exe.xml file:

<Launch.Addon>
<Disabled>False</Disabled>
<ManualLoad>False</ManualLoad>
<Name>TDS Sim Software GTNXi Gauge Integration</Name>
<Path>C:\ProgramData\TDS\GTNXi\FlightSimEXE\TDSGTNXiFlightSimEXE.exe</Path>
<CommandLine>-FSIntegration</CommandLine>
<NewConsole>True</NewConsole>
</Launch.Addon>

The location of the exe.xml file of MSFS is usually located here for MSFS Store version:
C:\Users\%username%\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache

where %username% is your username.