We’re thinking about redesigning our homepage, and two SEO-factors (favoring a website structure that is shallow or deep, respectively) are in conflict:

A. How quickly does SE-rank decrease when a page is deeper inside a website structure?
I’ve read that if the homepage is “first level” the pages it links to are second level, and pages these link to are third level, and so on. I assume a SE will consider second-level pages to be more important than third-level pages, and if all other things are equal (like keywords in the title,…) a second-level page will get a higher rank than a third-level page. But HOW MUCH does SE-status decrease with pages that are deeper inside the website structure, as the “level” increases from 2 to 3, 4,…? Is there a way to make an approximate estimate about the amounts of decrease?

B. How quickly does link-value decrease when the number of links on a page increase?
If two external pages with equal SEO-status link to my page, but one external page includes 10 total links (mine plus 9 others) and the other has 100 links, for improving my SE-rank does the first count 10 times as much because my link is 1-of-10 (= .10) not 1-of-100 (= .01)? Or is it more like an inverse logarithmic scale where there is 2 times as much credit by comparing 10 (which has log = 1) with 100 (log = 2)?
I assume a similar “numerical dilution of link-value” occurs with internal links within a website, but is the AMOUNT of dilution similar for these internal links and for external links?

By the way, I realize that you don’t know the mathematical SE-algorithm formula, so exact numerical answers aren’t possible. The numbers in B are just to define two extremes (ranging from a dilution of 1/10 to only ˝ for this example) but what I’m looking for are “guideline principles” about the relative importance of factors A and B, since typically they’re in conflict because…

If we focus on A, a good strategy is to make a “shallow structure” by linking to LOTS of pages from our homepage, so all of these pages become level-2.
But due to factor B each of these are a “diluted” level-2 that isn’t as strong as if we made half as many homepage links, or 1/4 as many, or 1/10.
So if we focus on A, 100 links seems best (with shallow structure). But 10 links (for a deeper structure) will be better if B carries more weight with SE-ranking.

Regarding the human factor and making the website good for people, either way (emphasizing A or B) we can design the website so users will know what content is available and how they can find it. But is either strategy better for SEO?