as far as I am aware there is NO COS 13 zip for the crackling, only this incremental update (ie an update from 12.1, so that needs to be installed as a base first and then the update flashed from recovery)
There is CM 13, both snapshots and nightlies that an be flashed from TWRP as ZIPs
TWRP an be flashed from fastboot whenever you like, so that shouldn't cause you any major concerns 
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