Small correction: use AlmaLinux 9 or Rocky Linux 9, not CentOS Stream 9. Stream is upstream of RHEL now, not a downstream clone. For RHCSA prep you want behavior as close to RHEL as possible. Alma and Rocky are 1:1 binary compatible.
Also: document your lab publicly. Blog, GitHub, whatever. I have reviewed hiring packets where the GitHub repo with 50 commits of "broke GRUB, fixed GRUB, broke it again" was more persuasive than the cert itself.