As per my point of view EX407 is easier than EX294 (RHCE RHEL8). All you need is to practice all guided exercices and lab exercises by your own several times and finally comprehensive review.
That is more than enough after you read all chapters and theories. Use of ansible doc and docs.ansible.com is really important.
I've faced both exams mntioned above and got passed already.
I still have the Voucher and to take soon, i am studying with the RHLS (Course is out, use the EX294 Labs now) and the Kodekloud Course for it. One Important Question is how much Documentation is available or do i need to know all params in mind? In CKA / CKAD i was able to use the full K8S Documentation. Is it the same on this Exam for the Ansible Documentation or just ansible-doc on Command Line? At the moment i feel strong in some subjects bad bad on others where i need to use the Docs for, just want to know if its good to do the Exam now before the Voucher expires