My Helix is similar to yours; but in a double N Scale Double Kato Unitrack at 30' and 28" radius in a oblong shape at a 1.5% Grade. For now the straights carry all of the grade and the Helix flattens out into the curves. The overall dimensions of this N Scale Helix is 63 x 96 inches. (about the size of a Queen Sized Bed.
Each level is constructed on four modules, which are held up by all threads. Each module is 1 1/2 inches thick with 5 mm triply facing on both sides. Squared to the outside but rounded to the inside, like a football/track field; as found at a High School.
As for my bus lines...
Kato Drop down leads every 90 degree Quarter Radius approximately every 36 inches. And one drop down lead per straight module.
That is six drop down leads per level.
> Yes, I solder each section as well. Being very careful to set each section flat with top rail to top rail leveling. I clamp each two sections to either marble or steel strip as I solder, then go over the finished/soldered rail with a variety of files, both on top and the insides.
These plug into Kato Blue Boxes which have been opened up and 12 gauge color coded wire soldered through them.
I have only tested this arrangement and do not have it currently in an operational layout.
The Kato Track was to be set upon CCW-705 underlayment which quiets it up substantially on a sub-strand level.
For now I do not totally solder my track. Instead, i put a toothpick slice of Dielectric Grease between each snap section; as I test.
This Helix was to be part of a three tier multi-connected layout in a large basement....but I have moved, my sleeping arrangements to a another location which also sports room for a layout. So My Helix basically sits in the basement as storage for now.
Sounds to me you have a good clue on what to do already.