Guys, the irony is that since H.264 it is purely optional to use a certain frame rate. The display time stamps (which were present in older codecs as well, but with a fixed delta) dictate how long a frame shows on the display device. That means you can mix and match any FPS without conversion and jumpy playback.
Now in practice the Blu-Ray still demands constant frame rates and video editors are also slow to adapt. It is likely that the upper price segment already offers solutions there, but not PD12.
I think there is still a working solution if you are fine with playing the video from a laptop connected to the TV instead of a Blu-Ray player...
Render each section that contains clips in a different frame rate separately. This way you can chose or create a matching profile for 25/30/60 FPS and possibly even utilize SVRT on each as a bonus. These parts can then be concatenated (lossless) with a variety of command-line and GUI tools, many of which are free (ffmpeg, AviDemux, VirtualDub, ...).
For fixed frame rates though, you can just stick with what PD offers. It was working a lot better for me (23.97 FPS material in 50 FPS timeline) than the demo version of VideoStudio, which targets a similar price segment.
(Hint: Since I haven't tried this, I don't know how PD handles any overhang resulting from selections on the timeline being 25 FPS and then rendering them in 30/60 FPS. So better make sure the 30/60 FPS segments' durations can be expressed in 30/60 FPS without rounding. That's easy if you measure them in whole seconds. In cases where that's not possible, select a multiple of 5 frames (resulting in 6 or 12 frames for 30 and 60 FPS respectively). You can verify the duration below the preview on the production tab: If it ends in a 5 or a 0 you are good to go!)