Frame rate and frames per second - mixing in same timeline (and some tilt-shift advice)

I'm thinking out loud here, so help me if it's wrong.

I'm confused. I'm shooting a timelapse in 24fps. 10 second clip, 240 images. For the next sequence I want 30fps. So I shoot 300 images. 30fps gives me a smoother timelapse, right? Then my buddy says he's short on time, so I do 15fps for the last sequence. 150 images in 10 seconds. This will give a more choppy sequence? Every images lasting twice as long as the 30fps sequence? Right?

Back home I want to show my friend the difference between 24fps and 60 fps. The timeline is set to 24fps. But dropping 600 images in the 24fps timeline gives me 25 seconds sequence, in 24fps. Do I have to create a 60fps timeline, render the video, and then drop the 60fps clip in the 24fps timeline?

And lastly, going to make a tilt-shift-video (people, cars). It was recommended shooting timelapse with 1 second interval, and then produce this in 15fps. But will this look good? Isn't it better to shoot 1 second interval and produce in 24fps? Or burst mode (4-6 fps) and produce in 24fps? Both will probably give the sped (jumping frames) up effect?

I'll answer in 3 parts to match your 3 questions,

1: You are correct.

2: There is no way to play 60 fps in a 24 fps timeline, either frames will be dropped to make the video 24 fps, or the video can be slowed down to play at 24 fps. If you want to compare the two, you will have to do so in a 60 fps timeline, and make sure that the rate conform and or retime quality settings for the 24 fps clip are not set to either frame blending or optical flow.

3: For tilt shift video people like low frame rates because it lends to the unreality of the visual, and makes it look more like a stop motion video, which are often shot at lower frame-rates. I recommend that you do some testing of different frame rates and intervals and see what you like, as the choices are purely artistic, and completely up to you.

Hope this helps,
-Mark

I like to use this website to demo effects of frame-rate and shutter-speed:

frames-per-second.appspot.com