Math and Vector are the most used they should be in in the root node in the node menu.
You work faster with them available directly under node menu.
I just use search for everything. It seems the fastest, at least when you know what your looking for.
Hit space while in nodes display, does not display all nodes, and i find it works pretty bad instead.
use shift a and the top one is seach. I use that for everything I know the name of.
A direct shortcut for “search” would be cool.
Can we use space to directly access “search” ?
not really - in 2.79 it is a search for blender items - not necessarily for add on things.
in 2.8 the search is a second option from the space bar - unless they changed it again. - Animation nodes works with CTRL-a to go directly to search nodes but that is built into the add on.