How do the custom trait mods work? Are they safe?

I've never used that particular mod but I have used other CC mods and they've all worked great with no trouble/glitches. They'll give your sims skill and career boosts and the ones I've used also give emotions. I've used these two and they work well:

http://modthesims.info/d/569993

http://brittpinkiesims.tumblr.com/post/147893668100/the-sims-4-harry-potter-mod-pack-part-2-of-3