I think the 200 Mhz are compared to an average gaming PC, it's just supposed to show how slow code execution gets compared to what it would be without Securom (I think something about 20 times as slow would fit the comparison), I couldn't tell you any exact figures though
And Securom VM has got nothing to do with conventional virtual machines like Virtualbox.
It means converting code into something hard to restore, ie. code is transformed into something only Securom understands and converts it into actualy byte code executable by the CPU. While trying to confuse crackers they added random useless code, added shitloads of crc checks etc. Something as simple as a function call ends up as 20 VM instructions each consisting of 100 or more normal CPU instructions.