For your question about the cloths if the stat stacks, this is what it looks when you have multiple kinds of Clothing .. I have 8 types of Clothing as of now (Anbu, Go! Fukurokumaru, Wild West, Summer Youth Sai, Exquisite Silk, Yes! Master, Hot-Blooded Sports and Eternal Belief from reaching the 70k power) ..

For your second question about when is the best time to get the clothing, here's my post from previous/old thread about the clothing too ..

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