Correct form of a chapter reference [closed]

Here is what I do:

When referring to a chapter generically, do not capitalize it:

This chapter talks about the exciting lives of carrier pigeons.

Refer to the chapter about carrier pigeons for more information.

When referring to a specific chapter, capitalize it:

The exciting lives of carrier pigeons are addressed in Chapter 5.

There are other purported "style guides" and grammar advice available via web search saying the same thing, but notably the Chicago Manual of Style disagrees:

Chicago prefers to lowercase the parts of a book, even if they’re titled generically, so in running text we would refer to “appendix A.”

This NGram should be sufficient evidence that people usually use digits. If nothing else, it avoids things getting really tedious if you needed to refer to chapter one hundred and twenty-eight when writing about some truly weighty tome (or one with a lot of short chapters).

As regards capitalisation, I've no doubt people sometimes do it even in references within text, but I think it looks overblown and silly. Having said that, I would expect capitals if Chapter 1 was written as part of the actual chapter heading.

As FumbleFingers stated, NGram evidence suggests that digits are used more frequently. Adding the other options, this NGrams additionally suggests using capitalization even in sentences: