I went here,
and it's actually solved just about every issue (I get a glitched npc sometimes, but maybe one or two in the few hours I was playing it since using the launch options... played through the Shrouded Bunker twice, did all the extra board missions in wellspring, ran back and forth blowing bandits up in the Turino, did a few races, and am now about halfway through the dead city). Make sure to force Vsync as well. The commands I use in Steam are:
You can find all the info on the RAGE forums (link above), but I haven't had any lock up or texture problems since using these, so I hope that some of you can use this information to your benefit! Good luck!