My apology for my useless answer, I was just trying to help.
If you can send me the code of the Winforms app, I promise to look at it.
The setfocus and the Click are functions of the Edit Control in Windows and were found using .NET reflection at runtime by the compiler. Keys on the other hand is a TestComplete function that runs against the Edit control.
There are 3 different ways of connecting apps, I can't tell what you are doing by the 3 lines you sent, that is why I asked for more info.
First of all, I have Visual Studio 2019 and also 2017 and none of these 2 will run the project at all because of the line that says Connect.TC["Visiable"] = true; that code will only run by maximum in Visual Studio 2013.
Error: Cannot implicitly convert type 'bool' to 'AutomatedQA.script.var.VarDelegate'
I was curious why, so I reversed engineer the assembly AutomatedQA.TestComplete.CSConnectedApp.dll
Within few minutes, I figured out why ConnectedApps have been obsolete and no longer supported for the last 6 years. It is just a pure mess how they were marshelling the types.
As I said earlier, I do not recommend the use of ConnectedApps and I am sorry if that answer is useless again to you.
My recommendation is for you to use the TestComplete TypeLibrary for 64 bit and use the Integration Object to execute the tests