Yes, I've used them a lot. You have to download them separately, but it's just a zip file that you extract and then tell rawtherapee where it is. It has many films; I really liked Portra 400 for portraits.

I think you can also get the Fuji film LUTs, so if you shoot raw you can later pick whichever film simulation you like.

For live preview I usually set minimum contrast and saturation, to get wider dynamic range (on the preview)