"Would" is a conditional tense. Something had to happen before you "would" do something else. You will often see "would" used in a phrase that starts with "if" of "when". "When we were young, we would go to the pool on Sundays." "If the our clothes were dirty, we would wash them." If "would" is not in a compound sentence like these, there is usually an inferred time period, or condition underlying the conversation. "Would" can also be used as a question word. "Would you like a piece of cake?" "Yes I would."

"Used to" is you HAVE done this certain thing before. "Would" is you more of a you HAVEN'T done this before, but, you would like to. Yes, it kind of does express 'nostalgia'. **And your last sentence, "...is used to express nostalgia." 'Used to' can express present things too! ***Next time, go to 'Answers' and type this in as a question^^ Hope this helps^^ Have a nice day!