[Tex/LaTex] Subfigures with no vertical space and top left aligned letter

Question

I am trying to create an image composed of three subfigures that looks like this:

Key features I am trying to capture are:

• No vertical space between the subfigures
• Subfigure letters are in the top left hand corner
• I would like to be able to label the subfigures
  so that I can refer to them in text so I dont want to put the subfigure letters in their own subfigure
• as a bonus I would like to be able to control the aesthetics of the subfigure labels if possible

Looking at a couple of questions like this one or this one I have had a go but am not very familiar with this and cant get it to work. Here is a MWE that does not actually work as I get

LaTeX Error: No counter 'subfigure@save' defined.

which I gather is because the subfig and subcaption packages conflict???

\documentclass{article}
\usepackage{subcaption}
\usepackage[demo]{graphicx}
\usepackage{floatrow}
\usepackage{subfig}

\begin{document}

\floatsetup[figure]{style=plain,subcapbesideposition=top}
\begin{figure}
\centering

\sidesubfloat[]{
\begin{subfigure}[b]{0.8\linewidth}
  \includegraphics[width=\linewidth]{}
\end{subfigure}}\\[-2ex]

\sidesubfloat[]{
\begin{subfigure}[b]{0.8\linewidth}
  \includegraphics[width=\linewidth]{}
\end{subfigure}}\\[-2ex]

\sidesubfloat[]{
\begin{subfigure}[b]{0.8\linewidth}
  \includegraphics[width=\linewidth]{}
\end{subfigure}}

\caption{Test Caption}
\label{fig: my-label}
\end{figure}

\end{document} 

Any help is much appreciated.

Answer 1

Inspired by solution in sidesubfloats (to which your question is very similar):

    \documentclass{article}
    \usepackage{floatrow}
    \usepackage{graphicx}
    \usepackage{subfig}
    \usepackage{caption}
    \floatsetup[figure]{style=plain,subcapbesideposition=top}

    \usepackage[margin=70mm]{geometry}

    \begin{document}
        \begin{figure}[h]\centering
    \sidesubfloat[]{\includegraphics[width = 0.8\textwidth]{example-image}\label{fig:a}}\\[-1pt]
   \sidesubfloat[]{\includegraphics[width = 0.8\textwidth]{example-image}\label{fig:b}}\\[-1pt]
    \sidesubfloat[]{\includegraphics[width = 0.8\textwidth]{example-image}\label{fig:c}}
    \caption{Main caption}
        \end{figure}
Figure \ref{fig:myfigure} consist three sub figures: \ref{fig:a}, \ref{fig:b} and \ref{fig:c} ...
    \end{document}

Edit: Now I also succeed to managed referencing of sub figures (usually helps to read package documentations ...). Code above is accordingly upgraded/correct, and picture now show the referencing ...