Particularly for adult sex web conferencing you want and need moveable, adjustable cameras.Most Quick Time compatible apps allow selecting and switching between multiple video sources on the fly; Nice and Civil to Down 'n' Dirty.It also provides alot of webcam effects to play with.
If webcam chat or capture is important to you, spend your money on a new Mac first.
UVC web cameras that DO work on a Mac don't come bundled with any OSX webcam software to control or adjust the image brightness or color.
And unfortunately, Apple doesn't have a Webcam Preference Pane in OSX.
There's several other Mac webcam effects and image apps worth checking out as well, notably Mactaris' Mac webcam app utility downloadable from the Apple App Store. If your processor is a G4 or greater, if it's speed is 867mhz or faster, that's the point where Apple built-in USB 2 speed ports. In Apple System Profiler Device Tree -- USB 2.0 devices listed need to show "Speed: 480Mb/sec".
Old USB 1.1 ports-devices will only show "Speed: 12Mb/sec" as thier maximum bandwidth. Modern USB 2.0 high-resolution UVC webcams utterly overwhelm USB 1.1 ports which are more than FOURTY TIMES SLOWER.