Here is our first attempt at codifying a guide for style, development, and testing of EVM-smart contracts at Coinbase. https://github.com/coinbase/solidity-style-guide

Our goal is to build the best Solidity organization in the world and documentation like this is an important start :)

Think you should add a comment clarifying imports declared at file level which you don't address. 

As in is it permissible to have an unnamed import if what you're importing is at file-level or don't declare anything at file-level and import it at all?

Hmm even if at file level, like a struct at file level you should use a named import? Is there something I’m not thinking of?

Hmm that’s a good Q. But yes I think named still preferred.

As in if you have all you structs and errors defined at file-level in one file, do you think named imports should be preferred regardless of length?

import {
  Struct1,
  Struct2,
  Struct3,
  ...
  StructN,
  Error1,
  Error2,
  Error3,
  ...
  ErrorN
} from "lib.sol"

as opposed to 

import "lib.sol"