Which option to use - drop-frame timecode OR non-drop ?

I agree with Ann.  Fixed frame rate is usually better for editing in any editor.

That said, PrE 2021 is supposed to work with variable frame rate footage from phones.  I've tried it and it will, depending on the source. 30.08 fps is not common!  So, consider trying it!  It may work fine.  

You can't change it in General Settings once the project is underway.  It is supposed to automatically pick the appropriate settings when you put the first clip on the timeline.  It usually works!

As this is phone footage with variable framerate and to avoid issues.

Convert with Handbrake to constant framerate before bringing it into Elements.

When imported drag the clip into an empty project and settings will adjust automatically to match the clip.

Converting videos with Handbrake - YouTube