Regarding your first point, in side projects, I've started doing things like this:

  for c in customers:
    return c.first_name + c.last_name

or:

  customers.map(c => c.first_name + c.last_name)

I've started doing this because I didn't like having "customers" and "customer", I found this very un-readable. It also makes it simpler to follow what's going on since I have less code to parse.

And because I never use 1-lettered variable names (unless it's a counter like i, j, k), I find it very easy to read when this convention occurs in my code.