Cannot center pdf image

Question

I'm using sharelatex and pdflatex as a compiler. I am using the memoir class. (It's for a book.)

At first I used .png images but the compiler always took too long so I converted all my image files to .pdf in order to gain a smaller file size=faster compilation speed and I realized that vector images' quality are better than raster so I want to keep working with vector formats (and I didn't use .svg or .eps because sharelatex doesn't support them).

The image has to fit the page's width margins (for the vector image) or if it does ever exceed, it can be floated(but still centered; and again, I used this trick for png images but they were too big and never loaded properly).

I've tried many solutions, but none of them managed to work. They used to work when the extension was still .png. But once I've switched to pdf they're all broken. (or worked differently so I didn't got my results).

I'm going to add the document's frames so it'll be easier to get an idea of how much the image is off-bounds to the center.

\documentclass[14pt]{memoir}
\usepackage[utf8]{inputenc}

\usepackage{graphicx}
\graphicspath{ {images/} }

\usepackage[paperwidth=6in, paperheight=9in, margin=0.9in, showframe]{geometry}

\begin{document}

\begin{center}
\includegraphics[scale = 1]{001}
\end{center}

\end{document}

Which got me this:

\documentclass[14pt]{memoir}
\usepackage[utf8]{inputenc}

\usepackage{graphicx}
\graphicspath{ {images/} }

\usepackage[paperwidth=6in, paperheight=9in, margin=0.9in, showframe]{geometry}

\begin{document}

\begin{center}
\includegraphics[scale = 1]{001_pngversion}
\end{center}

\end{document}

Result:

Which gives me the high resolution png version. Somehow, it looks like more aligned to the left...? Maybe it was because it's too big, it exceeded the page limits and couldn't center properly?

I then decided to use the \centering trick and the \linewidth trick to resize it:

\documentclass[14pt]{memoir}
\usepackage[utf8]{inputenc}

\usepackage{graphicx}
\graphicspath{ {images/} }

\usepackage[paperwidth=6in, paperheight=9in, margin=0.9in, showframe]{geometry}

\begin{document}

\begin{center}
\includegraphics[width=1\linewidth]{001}
\end{center}

\end{document}

Which got me this, the exact result I was looking for:

Now, let's try the same trick with pdf images:

\documentclass[14pt]{memoir}
\usepackage[utf8]{inputenc}

\usepackage{graphicx}
\graphicspath{ {images/} }

\usepackage[paperwidth=6in, paperheight=9in, margin=0.9in, showframe]{geometry}

\begin{document}

\begin{figure}
\centering
\includegraphics[width=1\linewidth]{001}
\end{figure}

\end{document}

Results:

Which obtained the same exact result as the FIRST ONE (failed one)

I then tried \begin{figure} \begin{floatrow} or \centerfloat , etc but it still failed. Only worked for pngs...

What I want to achieve is the result I got from the png version, while using .pdf images.

(On a side note, could someone explain the difference in using /centering, /centerline, and /centerfloat? While I was looking for answers concerning centering floating images that surpassed the page's margins. Which one is usually recommended?)