There are two different tools. KM100 is a key tool and the im508 is a key programmer.
The km100 can generate remotes, chips and a lot of other things related to keys and remotes.
The km100 has key programming also with the PLC200 interface, not as extensive in coverage as the 508 does thou. Check Autel KM100 vehicle coverage
KM100 contains MaxiVCI VCI200 so you can perform key simulation and key learning after generating a key.
It uses the USB cable to transfer data from another device, such as IM608, to a laptop and from the laptop to the key tool.
Km100 seems a bit faster device, can simulate chip, it is same as im508 for immo but without programmer. For universal remotes, xp400pro got update and also can generate autel remotes. Either im508 or im608 can generate autel smart keys now.
km100 is more of a key generator and the 608/508 is more for actual immo programming and diagnostic and a huge difference in price.
km100 enjoys lifetime free updates, im508 does require an annual subscription.
KM100 is pretty much the im508 without the xp200/xp400. I haven’t come across a car that the 508 can do that the km100 can’t.
People says it’s easier than getting 508 out. It even precoded and programmed a fiat key.
km100 seems to need internet more then my 508 does.
In a nutshell, the km100 seems to be targeted more at car sales, recovery and smaller businesses without a lot of experience.