Beginner's experience with React - a shout for feedback

Hi there!
I'm a react beginner and not really sure if this is the right place to post a call for feedback. I want to share my experience writing my first web app with react. It's a weather App inspired by This Post by Hamed

You can find the app here : MiniWeather.ms-mousa.now.sh and the codebase here GitHub

A quick breakdown of the app:

First Screen can show weather in 4 locations with 4 cards that have different background colors based on the temp in that location.

On hover, the card pops up and a "MORE" link shows up:

Second screen shows the detailed forecast in the next 4 days in that location:

Before you read my next words, last time I did something for the web JQuery was the HOT THING! So kindly keep that in mind!

Things I need feedback on:

• Component structure!

I think I should have done one from the start. I eventually had to do that. But it was difficult to do at the beginning cus I kept adding new things to it slowly. And will still develop a third screen. Yet, I DID spend hours rethinking my app structure.
The current structure is like this:

[APP] -> [WeatherEngine (API Input)] -> [WeatherCard(More link)] -> [ForecastEngine] (API Input ] -> [ForecastCard]
My main question is what is the right way to decide what should be its own component and shouldn't be?

• CSS-in-JS or not?

To start with, React components are not short! Like I needed to right many function to process the data from the APIs. Then I read about keeping the CSS inside JS and it would have made my components waaaaaay longer and less readable. What is the best practice for this? Keep it separate or include it in the component?

• Is it normal to have to write that much code?

I know this sounds silly, but it still seems a LOT of code just to structure a basic component and add some stuff to it. Am I doing it wrong? or this is the standard? Also the nesting seems a bit too much! functions inside component functions inside that API processing functions!

• What's the best way to 'ADD' a component on the click of a button?

What I ended up doing is to add a function (refer to my previous point) that switches a count variable and based on that shows two or three instances of the component. VDOM diffing works here for me cus when I add a new component, the old one stays as is. That still sounds like a very bad way to do it though. Any better ways? Here is my implementation:

 const [count , setCount] = useState(1);

  const show = () => {
    switch (count) {
      case 2:
          return (
            <div className='container' >
                <WeatherEngine/>
                <WeatherEngine/>
            </div>
          );
      case 3:
          return (
            <div className='container'>
                <WeatherEngine/>
                <WeatherEngine/>
                <WeatherEngine/>
            </div>
          );
      case 4:
          return (
            <div className='container'>
                <WeatherEngine/>
                <WeatherEngine/>
                <WeatherEngine/>
                <WeatherEngine/>
            </div>
          );
      default:
        return (
          <div className='container'>
            <WeatherEngine/>
          </div>
        );
    }

• This is more of a comment:

This idea of React has to return a div that contains other things and all results in too many divs! The markup has empty divs just to return two component togethers! So what's the best way to handle this?

• Is this the proper way to do conditional rendering? Looks off to me but works just fine!

return(
    <div>
     {
      //  render welcome screen to show the search component initially
       loading === null && cod === 0 ? //   matching the initial state
        <div className='welcome'>
          <Search getWeather = { getWeather } />
        </div>
       :
       loading === true ? // if loading is true - search button is pressed - show a loading icon
       <div className='loading'>     
        <i className='fas fa-spinner fa-4x spinner '></i>
       </div>
       :
       temp !== 0 && cod===200 ? // if temp is updated and cod is 200 as in successful API response
       <div>
        <WeatherCard 
          maxTemp = { main.maxTemp }
          minTemp = { main.minTemp }
          temp ={ main.averageTemp } 
          city = { city }
          country = { country }
          main = { weather.main }
          id = { weather.id }
        />
       </div>
       :
       loading === false ? // if loading is then error happend
       <div className="welcome">
         <Error cod = { cod } errorMessage= { errorMessage } />
         <Search getWeather = { getWeather } />
       </div>
       :
       <h1>dunno</h1> // we never get to this point so yeah dunno!
     }
     </div>

That's all!

Thanks for reading till here if you did! :)