\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\usepackage[version=4]{mhchem}
\usepackage{chemformula}
\setchemformula{
arrow-min-length=18.4pt,
compound-sep = {0.36em},
arrow-style = {line cap=round}
}
\RenewChemArrow{->}{\draw[chemarrow, ->]
(cf_arrow_start) -- (cf_arrow_end);}
\NewChemArrow{<-->}{
\draw [chemarrow, -Computer Modern Rightarrow]
([yshift=1pt]cf_arrow_start) -- ([yshift=1pt]cf_arrow_end);
\draw [chemarrow, Computer Modern Rightarrow-]
([yshift=-2.5pt]cf_arrow_start) -- ([yshift=-2.5pt]cf_arrow_end);
}
\RenewChemArrow{<=>}{
\draw [chemarrow, -{Computer Modern Rightarrow[left]}]
([yshift=1pt]cf_arrow_start) -- ([yshift=1pt]cf_arrow_end);
\draw [chemarrow, {Computer Modern Rightarrow[left]}-]
([yshift=-1pt]cf_arrow_start) -- ([yshift=-1pt]cf_arrow_end);
}
\begin{document}
\ce{A -> B} \ce{A <--> B} \ce{A <=> B}
\ch{A -> B} \ch{A <--> B} \ch{A <=> B}
\end{document}