Layout package modifies float figure behavior

Question

I have been working in a document where I need to load the layout package in the preamble and then my document also includes several figures with sub figures in each. The sub figures are identified by (a), (b), etc tags that I put with \put(x,y){(i)} command. So far so good, but I just realized that whenever I don't load layout package the position of the tag changes. Why is this and is there a way to fix this without manually change the coordinates options of each \put(x,y)(i)?

here mere examples of what happens:

\documentclass[12pt]{article}
\usepackage{geometry}
\usepackage{tikz}
\usetikzlibrary{matrix}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\usepackage{lmodern}
\usepackage{graphicx}
\usepackage{layout}
\begin{document}
\author{}
\layout
Inserting a Figure with subplots

\begin{figure}[htbp]
    \begin{center}
        \includegraphics[width=0.5\textwidth]{figa.pdf}\put(-30,160){(a)}
        \includegraphics[width=0.5\textwidth]{figb.pdf}\put(-30,160){(b)}
        \caption{Caption.}
        \label{default}
    \end{center}
\end{figure}

\end{document}

and its result

and with no layout package

\documentclass[12pt]{article}
\usepackage{geometry}
\usepackage{tikz}
\usetikzlibrary{matrix}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\usepackage{lmodern}
\usepackage{graphicx}    
\begin{document}
\author{}

Inserting a Figure with subplots

\begin{figure}[htbp]
    \begin{center}
        \includegraphics[width=0.5\textwidth]{figa.pdf}\put(-30,160){(a)}
        \includegraphics[width=0.5\textwidth]{figb.pdf}\put(-30,160){(b)}
        \caption{Caption.}
        \label{default}
    \end{center}
\end{figure}

\end{document}

Answer 1

You seem to be loading tikz anyway. If you compile

\documentclass[12pt]{article}
\usepackage{geometry}
\usepackage{tikz}
\usetikzlibrary{positioning}
%\usepackage{layout}
\begin{document}
\author{}
%\layout
Inserting a Figure with subplots

\begin{figure}[htbp]
\centering
\begin{tikzpicture}
\node[label=above
right:(a)](a){\includegraphics[width=0.45\textwidth]{example-image-a.pdf}};
\node[right=3mm of a,label=above
right:(b)](b){\includegraphics[width=0.45\textwidth]{example-image-b.pdf}};
\end{tikzpicture}
\caption{Caption.}
\label{default}
\end{figure}

\end{document}

you will get

regardless of whether or not you activate layout.