multi-alignments, any better solutions?

multi-alignments, any better solutions?

Please see my questions in the codes:
\documentclass{article}

\usepackage{amsmath,amsthm,mathtools}

\begin{document}

I am not sure align at the equal sign is a good idea, it looks weird to me.
\begin{align}
y & = \Sigma aaa \\  \nonumber
& = bbb + ccc \\ \nonumber
& + ddd + eee \\ \nonumber
& + fff + ggg
\end{align}

So I am trying some other options, like this,
\begin{align}
y= & \Sigma aaa \\  \nonumber
= &bbb + ccc \\ \nonumber
&  {\rm{~~~~}} + ddd + eee \\ \nonumber
&  {\rm{~~~~}} + fff + ggg
\end{align}
That is the first line and second line, align at equal sign, and the second and the rest, align at plus sign.

Or this,
\begin{align}
y= & \Sigma aaa \\  \nonumber
= & {\rm{~~~}} bbb + ccc \\ \nonumber
& + ddd + eee \\ \nonumber
& + fff + ggg
\end{align}
That is the first line and second line, align at equal sign, and the second and the rest, align at characters sign, and in the meantime, keep plus sign not aligned with equal sign.

Some sentences. Some sentences. Some sentences. Some sentences. Some sentences. Some sentences.

Some sentences. Some sentences. Some sentences. Some sentences. Some sentences. Some sentences. Some sentences.

\begin{align}
y= & \Sigma aaa \\  \nonumber
= & \rm{~~~} bbb - ccc - ddd - eee \\ \nonumber
& - fff - ggg
\end{align}
I want this new equation aligned with the above equations without using intertext.

Questions:

1) Using \emph{rm spaces} looks stupid and not always correct, any better solution for multi alignments?

2) How to align across different paragraphs, if I do not want to use "inter text"?

\end{document}