There is a minimum amount of active chemicals that needs to be in the mix for each square unit of film. Other than that, there is no difference.
The amount of chemistry needed is usually stamped on the bottom of your developing tank. Use the amount listed and don't worry. Time and temperature should be per manufacturer's spec until you have enough experience to be able to judge your negatives and decide if you want to vary the amount of time. Again, just do what the instructions say.
Condenser versus diffuser... Don't even worry about it.
Condensers produce more contrast, all other things equal, but you don't even need to think about that yet. When you make a print on an enlarger, there is no set time for exposure. Exposure time is determined empirically for each negative. No two negatives will print exactly the same. For contrast, you're going to determine that, empirically, for each negative, too. You'll use different filters or settings on each negative.
Not to sound rude... but... I think you're putting the cart before the horse.
The best thing you can do for yourself, right now, is to go get some film and soot some pictures. Develop them and look at the results.
Until you do that... Until you get some film in your hands, you're basically just spinning your wheels in the sand.
Like the advertisements say: "Just do it!"