PHP cache

[zebrafilm]

IIS is offering a wincache /PHP cache that speeds up loading PHP sites a lot.

I noticed that Plesk installs the thread safe version, Microsoft, normally installs the non-thread safe version which is also required for using the wincache extension.

question 1:
Why does Plesk installs the Thread-safe version?

question 2:
Is there any risk if I use the Non thread-safe version?

question 3:
Why doesn't install Plesk options like wincache?
(It makes sometimes 40% speed diff.)