Sentence 1 is what we call conditional type 2. We use If+simple past(were)+<would+infinitive>( would be). Here It is possible but very unlikely that the condition (be taller) will be fulfilled.
Sentence 2 is an example of conditional 3. We use If+ past perfect(hadn't had)+<Would+have+past participle>(wouldn't have become). Here It is impossible that the condition will be fulfilled because it refers to the past.
Hope that helps.