I think the helix section has 1 too many 'laps'. Helai are 'fun', but not for long. Personally, I only do 1 lap at the very most for a helix.
If you find that you have to have excessive helai, perhaps consider if your lifthill is too high. Lifthills higher than needed often gives the train too much speed, which means you may have to include aesthetically unpleasing elements just to eat up the speed, or throw in dodgey breaks. With coasters 'less is more'. But you can get away with 'more' if it looks good.
It's not uncommon to do an initial layout, and then modify it quite heavily. If you see on my thread with 'duelling insects', you can see a drastic difference from the 'completed' layout and the 'teaser' image. I basically removed 1/3 of the lifthill. This allowed me to create a better looking layout that wasn't too busy on the eye. It also meant it didn't end abruptly. Conversely, on a layout I have only teased about, but never showed off 'complete' (the B&M red one with smoke), I removed 2/3 of the layout entirely. I did some really weird things with it originally. Ingenious ideas, but practically didn't work. Even then, during the revision, I had to 'iron out' a section due to the intensity of the section.
I understand that your coasters which you share with us are 'stand-alone concepts' with no intention for terrain/scenery/theming. However, if you 'smoothed' out the pits the coaster forms, or gave them a better form, then it would look better. It makes the world the coaster set in look very mine-crafty due to the cube nature of the excavation. You can use the 'snap terrain' tool or manually tweak it easily.
Seeing what other people do with your chosen coaster type can be helpful. I don't mean copy them. It's good to be unique, but seeing what other people can achieve can broaden your own ideas. Perhaps you can take someone's unique aspect and take it in a new direction.
