It isn't wait before launching avast, but checking for updates, if that is what you mean ?
There isn't a wait xx time before launch at logon function/option.
Have you checked to see if these browsers are actually not supported, e.g. browse with them and see if the web shield is actually scanning content ?
If it isn't then it is OptinProcess=executablefilename.exe,executablefilename2.exe, etc.
[WebScanner]
OptinProcess=executableFileName.exe
I believe the Case is crucial in the OptinProcess name, additional processes being separated by a comma.