To change the reported guest OS:
In the vSphere Client inventory, right-click the virtual machine and select Edit Settings. Click the Options tab and select General Options. Select a guest operating system type and version. Click OK to save your changes and close the dialog box.
Please try the Web Client to configure the Red Hat 7 VM for the correct OS and report back if this doesn't show the option for RHEL either and post the build number of your ESXi host.