I am not sure about the alignment that you desire; perhaps something like this?
\documentclass[english]{scrartcl}
\usepackage[T1]{fontenc}
\usepackage[latin9]{inputenc}
\usepackage{array}
\usepackage{multirow}
\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% LyX specific LaTeX commands.
%% Because html converters don't know tabularnewline
\providecommand{\tabularnewline}{\\}
\makeatother
\usepackage{babel}
\begin{document}
\begin{tabular*}{1\columnwidth}{@{\extracolsep{\fill}}>{\raggedright}m{0.33\columnwidth}>{\raggedright}m{0.33\columnwidth}>{\centering}p{0.33\columnwidth}}
Column 1 & Column 2 & Column 3\tabularnewline
\multirow{2}{0.33\columnwidth}{Category 1 With very long text that wraps} & Subcategory 1.1 & Value 1\tabularnewline
& & Value 2\tabularnewline
& Subcategory 1.2 & Value 3\tabularnewline
& & Value 4\tabularnewline
Category 2 & Subcategory 2.1 & Value 5\tabularnewline
& Subcategory 2.2 & Value 6\tabularnewline
\end{tabular*}
\end{document}
I don't think there are many standard styles of coding outside the world of C/C++ and languages with C-like syntax. In fact, the styles you named in the questions are all C styles. I cannot recall any named styles for lua, PHP, Lisp, etc. There certainly are styles widely used for many languages, but except for C/C++, you can hardly find any "style guides".
TeX, whose syntax is quite unique, does not really has a style. It is perhaps even impossible to define a style in my opinion. For example, in C, someone (I think it is Linus) once said if your code has three or more nested levels, then you should redesign it. However, for TeX, it is not uncommon for a math formula to have many levels of brackets and one needs to deal with those long formulas, i.e., how to break them into lines, where to align them, etc. It is hard to define clear rules to be applied for all situations in the TeX world.
But readability of the code is still very important: this is the reason styles were invented in the first place. In my experience, alignment is perhaps the most important tool to improve the readability of TeX code. In fact there are tools, for example the Align plugin for Vim, available to make this task easier. And indentation is just as important to TeX as it is in other languages. I just don't think it is better to define a consistent rule for all TeX code. Instead, I believe TeX is more close to human languages and requires us to improve its readability based on the context.
Best Answer
If you want to edit the LaTeX source, then LyX is the wrong tool. Use one of the LaTeX editors, e.g. TeXworks, TeXmaker, aso. LyX can only edit it's own file format which of course can have some part of LaTeX code, called ERT (Evil Red Text), but that is also part of the LyX file.