In your case, when you just select a single property, the easiest way is probably to bypass any formatting altogether:
get-qadgroupmember 'Domain Admins' | foreach { $_.Name }
This will get you a simple string[] without column headings or empty lines. The Format-* cmdlets are mainly for human consumption and thus their output is not designed to be easily machine-readable or -parseable.
For multiple properties I’d probably go with the -f format operator. Something along the lines of
alias | %{ "{0,-10}{1,-10}{2,-60}" -f $_.COmmandType,$_.Name,$_.Definition }
which isn’t pretty but gives you easy and complete control over the output formatting. And no empty lines 🙂