Which of the following ways of writing equations is acceptable and/or preferable in mathematical typography?
\section*{Format 1}
The four equations in the computation graph are:
\begin{align*}
a_1 & = f(W_1 a_0 + b_1). \\
a_2 & = f(W_2 a_1 + b_2). \\
a_3 & = f(W_3 a_2 + b_3). \\
a_4 & = f(W_4 a_3 + b_4).
\end{align*}
\section*{Format 2}
The four equations in the computation graph are
\begin{align*}
a_1 & = f(W_1 a_0 + b_1), \\
a_2 & = f(W_2 a_1 + b_2), \\
a_3 & = f(W_3 a_2 + b_3), \\
\text{and }
a_4 & = f(W_4 a_3 + b_4).
\end{align*}
\section*{Format 3}
The four equations in the computation graph are
\begin{align*}
a_1 & = f(W_1 a_0 + b_1), \\
a_2 & = f(W_2 a_1 + b_2), \\
a_3 & = f(W_3 a_2 + b_3), \\
a_4 & = f(W_4 a_3 + b_4).
\end{align*}
Format 2 reads like it is closest to being correct English. But I think I have seen Format 3 more often in math books. Is there any consensus on which of these styles is correct and/or appropriate in professional mathematical typesetting?
Here are some related posts that I have already read but did not help me to resolve the answer to this question:
- https://mathoverflow.net/a/6683
- https://tex.stackexchange.com/a/170691
- https://english.stackexchange.com/a/22551
Note: I don't have any style guide I can look at to answer this question. I am writing for general audience. My PDFs may be hosted on my blog, GitHub, etc. I am trying to improve my typography style.

\intertext{and}instead of\text{and}. – Lei Zhao Apr 17 '21 at 15:20