Can someone explain what dry hopping and cold crash is please?
Terrym's summary on dry hopping is pretty much all you need to know.
Cold crashing is a method of speeding up maturation of beer. It's usually done soon after fermentation is finished, and the beer is reduced in temperature in a fridge. This does two things. It stops any further fermentation, which may otherwise slowly trickle on for quite a while, and facilitates the yeast dropping out of the beer to leave it clear. It also encourages "chill haze": this is usually caused by proteins in the beer, and can be a problem in beers that appear clear, but become cloudy when chilled for serving. Once the proteins have "gelled" at low temperature, they will settle out as long as the temperature remains low, and this can be speeded up by finings such as gelatine.
Neither process is necessary with all beers.
If you want a heavy hit of hop aroma, so that your beer smells powerfully of hops, then dry hopping is the only way to go. This can be either the American IPA styles, using very aromatic citrussy hops like Simcoe, Amarillo, Citra etc, but also for more British styles where Goldings or Fuggle can be quite dominant if used as a big dry hop addition.
If you don't want such dominant hop aroma in your beer, then don't dry hop. Try instead hop addition at the end of the boil, as the beer is cooling, to add hoppy flavour without such powerful aroma.
Cold crashing is entirely optional. I never do it. But, I'm happy to wait a month or so for my beer to clear before kegging. Also, I would never dream of serving beer below about 15°C. I do not subscribe to barbaric Antipodean or American practices, so chill haze is not an issue for me.