I'm not really sure what you're looking for here?
How does it end up different? it's exactly the same as a 5 gallon batch of beer, only a smaller amount. It's just an exponentially smaller amount of ingredients. If you are making a 1 gallon batch, then it's 1/5 of the amount of ingredients. If it is a 2.5 gallon batch, then it is half the amount of ingredients.
THough if you are using dry yeast just pitch the whole packet, and with liquid, for most grav beer, you really don't need to make a starter.
and if you like the recipe, you scale it up. Noting too complicated.
Fermentation times- I leave all my beers in primary for a month regardless if it's a full size batch or a mini batch.
Ag vs Pm vs Extract....it's not a verses, they all make beer, not matter what size you are looking for. Again it is simply exponentially less ingredients. ALthough one could argue it is easier to do small batches in All Grain. Though if you use DME instead LME for your base extract, then really there is no difference. Since you are just weighing out an amount of dry ingredients. It would be a wee bit more difficult, I think measuring out smaller amounts of liquid, and then storing the rest.
A digital scale is necessary, and I have found that for measuring out hops, having it being able to measure in grams makes things easier.
Anything else you want to know, you can find by looking at all the small batch brewing threads on here, there's a ton, and I have posted a lot of info in there.