Its smarter if you just install the SDKLite tools instead WestNZ, it installs much quicker, and the entire installation is self contained. I accidentally ended up installing the entire SDK Tools one time, and it took forever both to install and uninstall, unnecessary pain if you ask me. And yes, it is actually recommended to use the ATIV camera app for the time being as the MS Camera app is still a mess for us folks on the ATIV, and in some peoples opinion, for the entire WM community at large. So we're actually fortunate to have the native ATIV camera app work so well for us so far, even after the update and the difference in system/OS architecture now.
And I dont play Tetris Blitz so I cant comment on that or its performance. Sorry.
-- W