Unable to vertically align correctly long table

Question

I am using the package longtable and what I want to achieve is to have vertically centered cells, and equal row height.

I have tried using m{} column type, to achieve the vertical centering, but when I try to increase row height using arraystretch, the vertical alignmnent fails. So I need help in two matters

1. Why does arraystretch mess with the vertical alignment? How else could the functionality of arraystretch be achieved and keep the alignment?
2. Arraystretch does not give me equal row height but it only increases padding. How can I have equal row height?

Here is the output, you can see the difference in the arrow lengths:

MWE:

\documentclass{article}
\usepackage[table,dvipsnames]{xcolor}%table colors
\usepackage{array}
\usepackage{makecell}
\usepackage{longtable}
\setlength{\doublerulesep}{0pt}
\newcommand{\myhline}{\hline\hline\hline}
\newcolumntype{L}[1]{>{\raggedright\arraybackslash}m{#1}}
\newcolumntype{C}[1]{>{\centering\arraybackslash}m{#1}}
\newcolumntype{R}[1]{>{\raggedleft\arraybackslash}m{#1}}
\begin{document}
\begin{footnotesize} 
\renewcommand{\arraystretch}{3}
  \rowcolors{2}{MidnightBlue!10}{white}
  \begin{longtable}{ | C{1.7in} | C{1.5in} | C{0.65in} | C{0.6in} | C{0.6in} | }
 \hline
\rowcolor{MidnightBlue!30}
\textbf{test1} & \textbf{test2} &  \textbf{test3} & \textbf{test4} & \textbf{test5} \
  \myhline
  \textbf{qwerty} &  testing simple & - & + & + \
  \textbf{qwerty2} & testing simple long test & - & + & -\
  \textbf{qwerty} & testing simple long test & - & + & + \
  \textbf{qwerty} & testing simple long test & - & + & + \
  \textbf{qwerty} & testing simple long test & - &+ & + \
  \textbf{qwerty} & testing reaaaaaaaaaaaally simple loooooooooooooong test & - & + & + \
  \textbf{qwerty} & testing simple long test & - & + & + \
  \textbf{qwerty} & testing simple long test (pixels) & - & + & + \
  \textbf{qwerty} & testing simple long test & - & + & + \
  \hline
 \rowcolor{white} 
 \caption{Table testing} 
\label{my_label}
 \end{longtable}
\end{footnotesize}
\end{document}

Answer 1

(red lines indicate page layout)

Using cellspace (instead using of arraystretch)and xltabular (instead of longtable):

\documentclass{article}
\usepackage[skip=1ex]{caption}
\usepackage[table,dvipsnames]{xcolor}%table colors 
\usepackage{array, makecell, tabularx, xltabular}
    \newcolumntype{C}[1]{>{\centering\arraybackslash\hsize=#1\hsize}X}
    \newcolumntype{L}[1]{>{\raggedright\arraybackslash\hsize=#1\hsize}X}
    \newcolumntype{R}[1]{>{\raggedleft\arraybackslash\hsize=#1\hsize}X}
\usepackage[column=O]{cellspace}
    \setlength\cellspacetoplimit{5pt}
    \setlength\cellspacebottomlimit{5pt}
    \addparagraphcolumntypes{C}
%
%---------------- Show page layout. Don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\usepackage{lipsum}% For dummy text. Don't use in a real document
\begin{document}
{\footnotesize
 \centering
 \setlength\columnsep{4pt}
 \renewcommand\tabularxcolumn[1]{m{#1}}
 \rowcolors{2}{MidnightBlue!10}{white}
    \begin{tabularx}{\linewidth}{ |>{\bfseries}O{C{1.75}}|O{C{1.75}}|
                                               O{C{0.50}}|O{C{0.50}}|O{C{0.50}}| }
     \Xhline{1pt}
test 1  & \textbf{test 2}

            & \textbf{test 3}   & \textbf{test 4}   & \textbf{test 5}   \

     \Xhline{0.5pt}
qwerty  & testing simple            & - & + & + \
qwerty  & testing simple long test  & - & + & -\
qwerty  & testing simple long test  & - & + & + \
qwerty  & testing simple long test  & - & + & + \
qwerty  & testing simple long test  & - & + & + \
qwerty  & testing reaaaaaaaaaaaally simple loooooooooooooong test 
                                    & - & + & + \
qwerty  & testing simple long test  & - & + & + \
qwerty  & testing simple long test (pixels) 
                                    & - & + & + \
qwerty  & testing simple long test  & - & + & + \
     \Xhline{1pt}
    \end{tabularx}
\captionof{table}{Table testing}
\label{my_label}
}
\end{document}