Leon, both versions work fine. I use the Standard Toucam for guiding and don't have any problems finding a guide star.
The modded version will give you more stars to pick from, but either will be fine.
Alternatively, Bintel are selling the Meade DSI for the same price as a standard Toucam, and the DSI has long exposure.
No, you don't have to use an IR/UV filter as a Guiding program uses the centroid to guide on. Which means a star can even be slightly out of focus and will guide perfectly. The program centres on the source of light, not how sharp it is.
I tried it with an IR/UV filter and the brighter stars slightly faded and I completely lost the fainter stars. The exposure time isn't long enough to catch lots of light, so it is slightly affected.