Your wort kit is fine as it is. Other than fermenting it carefully, you don’t need to do anything to it but . . .
Dry hopping adds extra hop flavour and aroma. Some of the kits don’t need it, eg Black Lager, while for others it is recommended for the full expression of the style, eg XPA, Ultra Pale Ale. And for others, it’s just a nice touch.
Rates can vary from 1 or 2 grams per litre up to 10 grams or even more for styles like New England IPAs.
Generally you want to dry hop when the wort has finished fermenting, or is close to it. Dry hop at the fermentation temperature and allow three or four days of contact. You will need to decide whether you will dry hop as is, or use a hop bag or similar. Dry hopping as is will give better results but is messier. Using a hop bag is neater, but be careful not to overfill the bag as the hops will swell up.
If you are dry hopping at 1 gram per litre or less there is probably no need to change to your current procedures.
At higher rates you need to make sure the beer is clear enough to package, especially if you are kegging.
If you are fermenting at ambient temperatures, siphon the beer into another fermenter and leave the beer a few more days to clear up. Continue as normal.
If you have temperature control, cold crash the beer from about day three. When the hops and yeast have mostly settled, siphon the beer to another fermenter to clear before packaging.
If you have a conical fermenter, start dropping the spent yeast several days ahead of adding the hops. Late on day three start drop out some of the spent hops followed by more on day four. When you are satisfied you have reasonably clear beer proceed as normal.
New England IPAs have their own procedures. Hops are added in three or more charges over the course of fermentation. If you have a conical fermenter then drop out the hops from the previous charge before adding the next. If you have a flat bottomed fermenter you may need to transfer the beer two or more times so it is suitable for packaging – you do not want to be pulling our the beer dip tube from the keg to clean it every couple of beers.
In all of this, there is no hard and fast way to do things. Find a method that suits you and gives you results you are happy with.
Increase the alcohol
Brewing the wort kit undiluted will increase the alcohol and concentrate the flavour. With a start gravity of 1054 or so, you should get an alcohol content of around 5.4% ABV – more if you allow for bottle primings.
If you want to brew a higher alcohol style, eg Belgian ale, using the wort kit as a base, then adding up to 500 grams of malt extract, dextrose or sugar to the undiluted wort kit will not effect the balance of the beer too much. Remember malt extra, dried or liquid, tends to ferment sweet while dextrose and sugar will ferment out dry. If you want to add more than 500 grams then use a blend of malt extract and dextrose/sugar. You might also need to add some extra hops.
Reduce the alcohol
The wort kits will be fine if you want to make them up to 22 or 23 litres rather than the standard 20 litres. If you want to reduce the alcohol further then add some maltodextrin to bulk up the beer. Maltodextrin is typically only 30% fermentable, the unfermentable dextrins will add body to the beer. Make the wort kit up to about 25 litres, add 100 to 150 grams of maltodextrin and you should have a beer at about 3.6% with good body. You might need to add a little extra hops.
Change the yeast, change the beer
These wort kits have generally been designed with a particular yeast, or type of yeast, in mind. However, you can use different yeasts to produce different styles of beer. All of the kits can be brewed as either ales or lagers.
The Wheat Beer can be brewed with Safale US-05, rather than the Safwheat WB-06, to produce a wheaten ale. It can also be brewed with a saison yeast. And with the right micro-organisms it can be brewed as a sour beer, several yeast companies produce sour mixes.
The Kolsch too is similarly verstatile. Rather than Safale K-97, US-05 can be used to produce a neutral tasting golden ale. It can also be fermented cool with a lager yeast to produce a pale lager. It too will work well with a saison yeast or sour mix.
NEIPA it up
Two things define the New England IPA: yeast and hops. For this I will assume you have the right strain of yeast, eg Wyeast 1318 London Ale III. For a NEIPA the hopping is mostly whirlpool and dry hopping in the tank. There might be some first wort hopping. Typically little or no hops are added to the boil.
To NEIPA up a wort kit, pour three litres into a stockpot. Pour the rest into a sanitised fermenter and pitch the yeast. Add a litre of water to the wort in the stockpot and heat to about 90°C. Add 60 grams of a suitable hop and gently stir with a sanitised spoon. Sanitise the lid of the stockpot and cover to about 90%. Leave the wort to cool to about 80°C and add another 60 grams of hops. Place the stockpot in a sink of cold water to crash cool. Stir the wort again and cover with the lid. When the wort has cooled to pitching temperature or close to it, add it back to the fermenter.
NEIPAs should have plenty of hop flavour and aroma without being excessively bitter. The best kits to NEIPA up are the XPA and Ultra Pale Ale, followed by the Kolsch and Wheat beer. The American Pale and Amarillo ales would also work but could end up a little too bitter for the style.