For superscript citations there is \supercite (defined for all numeric standard styles).
There is no \subcite for subscript citations (not that I have ever seen that), but it can be implemented as a straightforward adaption of \supercite. Do keep in mind that the definition of \supercite is style dependent, so the code below only works for (cite)style=numeric-comp.
\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[backend=biber, bibstyle=ieee, citestyle=numeric-comp,
sorting=none, labeldateparts,
maxbibnames=99, maxcitenames=2, mincitenames=1]{biblatex}
\newrobustcmd{\mkbibsubscript}[1]{%
\unspace\allowhyphens\textsubscript{%
\begingroup
\protected\long\def\mkbibsuperscript##1{%
\blx@warning{Nested superscript}%
\mkbibbrackets{##1}}%
#1\endgroup}}
\DeclareCiteCommand{\subcite}[\mkbibsubscript]
{\usebibmacro{cite:init}%
\let\multicitedelim=\supercitedelim
\iffieldundef{prenote}
{}
{\BibliographyWarning{Ignoring prenote argument}}%
\iffieldundef{postnote}
{}
{\BibliographyWarning{Ignoring postnote argument}}}
{\usebibmacro{citeindex}%
\usebibmacro{cite:comp}}
{}
{\usebibmacro{cite:dump}}
\addbibresource{biblatex-examples.bib}
\begin{document}
Lorem\supercite{sigfridsson} ipsum\supercite{worman}
dolor\supercite{sigfridsson}
Lorem\subcite{sigfridsson} ipsum\subcite{geer}
dolor\supercite{sigfridsson}
\printbibliography
\end{document}

\supercite? But please try to give us a full minimal example code we can play with. I have a feeling you may actually want a bit more than that given your many loading options. – moewe Sep 19 '18 at 15:51