JSON print if other element exists with value

Input:

[{
    "VM": "__Total (All)",
    "MemConfigured(M)": "87",
    "DiskRead(IOPS)": 4322
},
{
    "VM": "__Total (All)",
    "MemConfigured(M)":  null,
    "DiskRead(IOPS)": 122
}]

Print 'DiskRead(IOPS)' if MemConfigured(M) is null:

$.[?(@.['MemConfigured(M)'] == '')].['DiskRead(IOPS)']

Print 'DiskRead(IOPS)' if VM = '__Total (All)' and 'MemConfigured(M)' is null:

$.[?(@.VM == '__Total (All)' && @.['MemConfigured(M)'] == '')].['DiskRead(IOPS)']