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Real confidence and empty bluster are two different things.
Literal
Real [genitive-の] confidence [and-と] empty-bluster [topic-は] separate-matter is.
An aphoristic declaration. 空威張り (からいばり) is a vivid compound: 空 (empty, hollow) + 威張り (acting important, bragging) = 'empty bluster,' 'hollow swagger,' 'pretentious posturing without substance.' 別問題 ('a separate matter,' 'a different issue') is a set phrase used to mark two things as not actually equivalent, despite surface similarity. Common in argumentative writing to draw distinctions: ~と~は別問題だ = 'X and Y are two different things.' The sentence is the kind of line you'd find in a self-help book or a parent's lecture.