Basically more surface area. The surface area and perforations go hand in hand for a film format. The noise in film is based off a unit area. So the grain is a physical fixed size. So the larger the negative the less noise is in any specific part.
So 5 perf 70 has about twice as much area as a 35mm negative and 15 perf 70 is 3x that.
All that means this will be a very noiseless movie.
Christopher Nolan goes through a significant amount of effort and time to hone his films. I find it hard to believe that someone who spends such effort specifically to make a film print and advocate for film distribution would do so for a format that he feels is inferior.
It's FotoKem :) We typically scan 65 as that is the negative format. 70MM is the print format with the sound track added.
The resolution of film is measured differently than digital. In the analog world you have line pairs/mm. Lots of the aspects of film that people strive to replicate in digital reduce the resolution. like grain and gate wave.
Film resolution, the ability to resolve detail, depends on the mechanical condition of the camera, the type of lenses uses, the quality of focus pulling, depth of field in a shot, motion of the subject, the type of exposure and lab processing.
If you notice many of these issues are not unique to film.
One you get to film printing you have the film processing, the quality of splices, the source element (cut o-neg or dup negative), the speed of the printing machine, the type of printing (wet or dry) and the mechanical condition of the printing machine.
Right now the amount of film getting made is small enough that it can all be short run quality. For the number of prints considered a distribution run today slower machines that allow for tighter tolerances can be used. Compared to what you may have experienced 30 years ago when thousands of prints needed to be made and shipped out on the same day the quality of any print is likely to be higher.
I haven't used fusion though I really should. Node based image generation is a revelation. Once you grok it you wish more image editing could be that way.
If you are comfortable with a program it makes sense to use it. They can all do the same things, just with different levels of effort.
There are a few sources that can be had for motion picture film. If you are looking for information in general you can look at "Student filmmaker's handbook" by kodak
I believe that Kodak has a free PDF available as well.
Other resources are going to be Kodak, and your camera rental house.
As well you can talk to the folks at Fotokem, film sales and they can help guide you though.
Why 35 and not 16?
I am not sure about the advantages of staying inside the ecosystem. There are typically some to staying in group of programs, such as the adobe suite.
Typically vfx are broken out and done before a color pass.
I would say until Adobe really up the ante on color Resolve is where you should finish your color passes. It has also become good enough to many editorial tasks on feature films.
I haven't seen effective VFX in resolve. After effects and Nuke are the two I've seen.
Those are my 2 cents