but i really worry about running it under wrong user level
Not many users start their installers using 'Run As Administrator' these days, and those who do, probably know what they are doing anyway.
Inno Setup triggers the UAC permission dialog at the expected/right moment, unless ofcourse UAC is turned off
I guess 95% of current Inno Setup scripts that has an executable that can be run right after installation, offers the option to do that.(I'll again admit I'm an Inno Setup addict/fan/advocate/12+ year user, but have no other bindings to it than that, and I like installers to be done 'just right')