Welcome to the forum!
Barry has covered some very important subject. I would like to discuss some other issues.
You are correct about the distortion. Most of the tonal distortion and tone shaping will occur in your pedals. Amplifier and speaker distortion occur after the pedals. For practice and small room venues, you can use a smaller amp in the 10-30 Watt power range. For use with a full rock band, you would want to have more power unless you are feeding a house PA system.
Since you are just starting with your first pedal build, I suggest you build each circuit and test it separately from the others. Once you have working circuits, then you can combine them into a combo enclosure. Careful planning of the physical layout of boards, pots, jacks and power is needed. Look at some of the photos posted to get some great ideas.