Guidance on RHEL Version and Planning Considerations

I am in the process of planning a deployment of Red Hat Enterprise Linux (RHEL) as a project at a college while we develop a datacenter program. We would like to install RHEL on a group of Dell Blade Servers consisting of Poweredge models m500, m600, m605 and m620. Could you please advise on the most suitable RHEL version for this hardware? Additionally, I would appreciate any guidance on other key considerations or best practices I should be aware of during this planning phase.