I would like to move a sim in to check routing and make sure objects on lots are usable. Is that safe? I have a lot of lots with object placements that look nice, but might not work in practice...I'm afraid of corrupting or damaging my CAW files.

As far as I know, EIG hasn't had that capability in a long time, unless they reinstated it in the SHT version. I read they had problems with it corrupting things. I did do it once when I first started CAW, with an ancient 2009 version and probably no patching after game installation. Just one lone guy running around my almost empty world...would be nice to have it again.

I usually export my world from CAW about once a week, install the Sims3pack and then move in some sims and make a savegame. Then I do testing of various things...

I would definitely export the world and test it in-game as PoisonFrog suggests, rather than attempting EIG. That way you can rapidly populate it and stress test it more easily. If you have Pets or LN, the main routing problems I've seen are from horses and bartenders spawning in stupid places, so running in EIG won't show you that.