The ini path by default checks $HOME/.mame/ first, then ./, then ini/ (on the Mac, it omits the first one and just checks the current directory and ini/). The file can be called either {exename}.ini (eg mamep4.ini) or just mame.ini (the latter is handy so debug builds can share the same config). It also will check for {drivername}.ini and {romsetname}.ini just like MAME/W.
Oh, and Voodoo DRC doesn't work on any version AFAIK (not even original Windows MAME). Don't try to enable it or the new debugger :-)