I don't get the meaning of syntactic structure but I guess yes there is equivalent in Chinese:
(1) Jenny 就是 Jenny
(2) 你/她不太像你/她(it's not that like you/she)
(4) 他是我，她是你（but we would probaly say 他演我，她演你）
I don't think there are any clauses. Both of them are verbs. The different tones express different emotions.
If you say "xiǎng xiǎng", you are emphasizing you are pondering. So you pronounce with stress. For instance, you are quarrelling with someone, and you said "Shut up! Let me think about it!"
And if you say "xiáng xiǎng", most of the time you are ...