Yea, that's a quite well known problem with PowerStrip on the forum, I'm sure you can find my thread asking the very same question back in September or something. And getting the same answer from everyone. (/t
I also asked "how do you know". Truth is, you don't. If you know where the source is from, you just "know". For example, I know that the movie "Star Wars II: Attack of the Clones" was in the theaters, and therefore on film, and therefore is a 24fps source. Meanwhile some PBS/BBC special is most likely 30fps video source because it wasn't in theaters.
A reasonable general rule is: shown in local cinema at some point: 24fps source. otherwise: who knows.

For the latter, try it at 24 fps, if it jutters bad, try 30 fps. I don't have any suggestions for the PAL sources, nor do I know what a PAL disc at 48 Hz would look like. Usually I see the jutter within the first 5 minutes of watching something and correct for it in a few seconds.
DScaler will tell you if it currently is seeing a 3:2 cadence and is correcting for it in its status bar. If you go full screen, you can look at the OSD screens to get that information. This might require enabling all 5 OSD screens, as not all are enabled by default.
TheaterTek 1.5 now finally will tell you the frame rate in the information OSD. (Use "I" not Ctrl-I.) Prior versions could not do this. Other DVD player applications may vary.
The good news is, if you just want to change the refresh rate while your watching a show or DVD, DScaler and TheaterTek will let you change the refresh rate while they are running. Just arrange for Girder to run PowerStrip command line in the background, running "Hidden". I have two remote keys setup, "48Hz" and "60Hz" and can jump back and forth. Sure there's a stutter as my Barco switches and syncs, but once its switched its steady. I usually only switch if I know I'll be at that refresh rate for at least 15 minutes, and the current one looks horrible.
I was pretty worried about getting the right rates too when I first started. Turns out, after a while, you'll quickly see what the 4 different possibilities looks like (well, for NTSC only) and can pretty much judge what the source is based on where it came from, and what it looks like on the current refresh rate.
Does this make any sense?
As for the WAF, two things: one, put the movie in BEFORE showtime, twiddle, and THEN invite her into the room. two: hide the remotes on yourself. Or better, offer her custody of them during the movie.
I had a
horrible twiddle finger reflex when I first got things setup. Kept playing with every control possible on the projector, or the HTPC. My wife whined, bitched, etc. Once I got things settled (or maybe it was me that settled), I only use the remote to power up the projector, and to power it down. She is much happier now. And I no longer have to offer her the remotes.
I only have to twiddle now for the odd DVD like "The Rock" which appears on my screen shifted right about 40 inches... and she accepts the 5 seconds it takes for me to correct it in TheaterTek's aspect ratio editor. TheaterTek is great because it will remember the correction on a per disk basis, so the next time we watch it the correction is not necessary.