How to use Gupl-cssnano presets (newbie question)?

Question

gulp.js

Hello!
Just started to learn Gupl and faced the need:

• minify final CSS file;
  
• remove (combine) duplicates in it
  
• set vendor prefixes for css properties (it is clear that Gulp-Autoprefixer is responsible for this)
  
• delete comments
  
• well, and everything else (so as not to paint a lot) that is needed for a normal final CSS file...
  

I rummaged through a bunch of information on the Internet, got acquainted with such plugins as: gulp-clean-css , gulp-csso , gulp-css-purge and of course gulp -cssnano itself ... I
opted for the last one - gulp-cssnano because .he has a lot of presets .
But! How to use them, at the office. I did not find the site (as well as on the Internet), except for one - discardOverridden: {removeAll: false}...
Tried by analogy:

.pipe(cssnano({
  autoprefixer: {browsers: supported, add: true, cascade: false, grid: true}, //работает. Остальное - нет
  discardOverridden: {removeAll: false},
  cssDeclarationSorter: {order: 'smacss'},
  //discardComments: {removeAll: false},
  discardComments: false,
  cssDeclarationSorter: false,
  mergeIdents: true
}))

but cssnano:

1. removes all media - (discardOverridden)
   
2. does not sort - (cssDeclarationSorter)
   
3. if I have several different classes with the same styles like:
   

   .popover-title, .popover-content{
       font-family: Verdana, Geneva, Arial, Helvetica, sans-serif
   }

   
   and
   

   body, label, select, input[type=text], textarea{
       font-family: Verdana, Geneva, Arial, Helvetica, sans-serif
   }

   
   then cssnano doesn't merge them together... For example like this:
   

   body, label, select, input[type=text], textarea, .popover-title, .popover-content{
       font-family: Verdana, Geneva, Arial, Helvetica, sans-serif
   }

   
   

In a word: plz tell me how to use it (if possible with examples)?
Unfortunately, my English is sooooo bad, but from what I could read, the thought creeps in on me that cssnano needs to be used with gulp-postcss ... or is it not necessary?
Thanks in advance for your replies !

Answer 1

CSSnano works dozens of times slower and is not the best choice in other respects. Use CSSO or gulp-clean-css with default settings - that's enough if you don't want to mess around with settings.

Answer 2

If you are using version 4 of cssnano, try specifying both preset and your options. For example:

.pipe(cssnano(['default', {
  cssDeclarationSorter: false,
  discardOverridden: false,
  discardComments: false,
  mergeIdents: true
}]))