Oops, I answered this yesterday and somehow my post didn't submit. Sorry.
- i have a project in v2.12 now (i use wybuild since the v2), but the preference in the wybuild project was "framework .net 2.0". What is the impact, if i change this to "framework .net 4.0" (which is the target framework for my software) for the next update ?
That's just the version of wyUpdate you'll be including with your app. Either the .NET 2.0 version or the .NET4.0 version. The impact of changing it is the wyUpdate.exe file will be different and the "self update" sites stored in the client.wyc file will be different.
The functionality of both versions is identical.
- why the parameter "optimize with NGEN" isn't check by default ? What is the problem or impact if i check this now ?
NGENing improves performance for some types of apps. Sometimes it's only a negligible performance increase. So test it out and see if it makes your app faster. If it does, enable it. If not, leave it disabled.