Can I do what I need to do just by using OLE?

Depends on how adaptive you are, see Re: I need to automate/scrape data from IE ( esp tutorials this collection of win32 tutorials/examples, On being a browser).

I guess, IEAutomation and Win32::Waitr use AutoIt because it saves you lots of work mixing Win32::OLE and Win32::GuiTest and whatnot, and AutoIt has a big community, so when you're stuck, you can ask win32 users who are automating win32, instead of figuring things out yourself