1. They are not "vulnerabilities" as such. Vulnerabilities belong to the operating system and applications that you run.I would like to add, are there many ASM based vulnerabilities that are intended for Intel, and therefore Apple's switch means a less secure platform?
2. Yes there is a lot of ASM malware that would only run in an intel/windows environment. However it is all very old, and Apple are retaining their operating system. I would say there is nothing to worry about.
The two dangers are that Apples suddenly become very cheap (which I doubt) and the market gets flooded with them
There is a very slight possibility that it might making cross-platform viruses slightly easier to write, but I don't really believe this, as I am sure Apple will get Intel to build the chips to their specification. I am also sure that they will use their own microcode, which is what matters.