How to center customised lof name?

How to center customised lof name ?

I need to control lof style. I need :

• lof name to be centered with given style (font, color, …)
• space after lof name
• centered line (not spanning the whole page)
• space after line

Trying this

~lof> more .lof.tex
documentclass[letterpaper,10pt]{report}
usepackage{fontspec}

newcommand{lof}{
  renewcommand{listfigurename}{%
    centering%
    fontsize{16pt}{18pt}selectfont textbf{MY LIST OF FIG}%
    newline%
    centering%
    vspace*{0.3cm}%
    {rule{3cm}{0.8pt}}%
    vspace*{0.3cm}%
  }
  listoffigures
}

begin{document}
lof
end{document}

gives

Which is not centered as expected. Trying this :

~lof> more .lof2.tex
documentclass[letterpaper,10pt]{report}
usepackage{fontspec}

newcommand{lof}{
  renewcommand{listfigurename}{%
    begin{center}%
    fontsize{16pt}{18pt}selectfont textbf{MY LIST OF FIG}%
    newline%
    vspace*{0.3cm}%
    {rule{3cm}{0.8pt}}%
    vspace*{0.3cm}%
    end{center}%
  }
  listoffigures
}

begin{document}
lof
end{document}

Does not help (getting exact same result).

UPDATE 1

This does not help either

~lof> more lof.tex
documentclass[letterpaper,10pt]{report}
usepackage{tocloft}
usepackage{fontspec}

newcommand{lof}{
  renewcommand{listfigurename}{%
    textbf{MY LIST OF FIG}%
  }
  renewcommand{cftloftitlefont}{%
    centering%
    fontsize{16pt}{18pt}selectfont%
  }
  renewcommand{cftafterloftitle}{%
    centering%
    newline%
    vspace*{0.3cm}%
    {rule{3cm}{0.8pt}}%
    vspace*{0.3cm}%
  }
  listoffigures
}

begin{document}
lof
end{document}

Which gives

UPDATE 2

Does not work either

~lof> more .lof.tex
documentclass[letterpaper,10pt]{report}
usepackage{tocloft}
usepackage{fontspec}
usepackage{textcase}

newcommand{lof}{
  newlength{lofnamel}
  renewcommand{listfigurename}{%
    my list of fig%
  }
  settowidth{lofnamel}{listfigurename}

  renewcommand{cftloftitlefont}{%
    hfillbfseriesfontsize{16pt}{18pt}selectfontMakeTextUppercase%
  }

  renewcommand{cftafterloftitle}{
    %
    vspace*{0.3cm}%
    centering {rule{3cm}{0.8pt}}%
    vspace*{0.3cm}%
  }
  listoffigures
}

begin{document}
lof
end{document}

Which gives

Franck

% loftitleprob.tex  SE 598988

documentclass[letterpaper,10pt]{memoir}
usepackage{fontspec}

usepackage{lipsum}

newlength{lofnamel}
renewcommand{listfigurename}{MY LIST OF FIG}
settowidth{lofnamel}{listfigurename}

renewcommand{printloftitle}[1]{%
  centering Largebfseries #1  rule{lofnamel}{0.1em}}

begin{document}
listoffigures

begin{comment} % stuff below adds text and a figure
lipsum[1]

begin{figure}
centering
FIGURE
caption{A figure}
end{figure}
end{comment}

end{document}