For JNCIP-ENT, you really just need to focus on the materials from the AJEX and the AJER courses. The labs are beneficial no doubt, but only to reinforce your learning of the subject matter. If you can practice the labs you will be in a much better position, but I would say it is also possible to pass by simply reviewing the materials.
I believe you only need the AJER and AJEX study material. Atleast that is all I'm using to prep for the JNCIP-ENT. The other troubleshooting study guides you listed (AJERT & AJEXT) are for the new Support Certification JNCSP-ENT.