Following a global preference for unpinning the left navigation sidebar, as of now, the preferences for enabling keyboard shortcuts and disabling the fixed topbar are network-wide* as well.
If you had either checked off on any site in the network, that setting has been preserved and applied to the whole network for your account already. Future changes will also apply to all* Q&A sites.
Find them in their usual spot as previously on the Preferences pages.
* With the exception of Ask Ubuntu, which will support the fixed topbar after the theme update.