how can i adjust the position at which the wire splits? and how to make a single wire splits into two wires seemlesly?

Question

for example, I have the wires that run from the node b_2 which I want it to split to both label_g2 and XOR1.in 1, currently, I have 2 things I don't like about it:

1. I have to do it with two different \draw functions and it looks like there's overlap in the first segment (rendering that part thicker)
2. the wire split is too far, I want to make it halfway between b_2 and the x position of XOR1.in 1 (without using exact coordinates)
3. I want to know if there's a way to automatically adjust nodes in relation to other nodes, for example here I've set the location of the g1,g0 nodes by hand, but I would have liked to have some way to make a straight line from the logic gate output (or whatever node) directly to g1/g0 generally.

\begin{document}

\begin{circuitikz} 

\node[anchor=base] (label_b2) at (-2,1.5) {$b_2$}; 
\node[anchor=base] (label_b1) at (-2,0) {$b_1$}; 
\node[anchor=base] (label_b0) at (-2,-1.5) {$b_0$}; 

\node[anchor=base] (label_g2) at (3,1.5) {$g_2$}; 
\node[anchor=base] (label_g1) at (3,0.26) {$g_1$}; 
\node[anchor=base] (label_g0) at (3,-1.24) {$g_0$}; 

\node[ieeestd xor port, scale=0.75] (XOR1) at (0.5,0.3) {};
\draw (label_b2) -|node[circ]{} (XOR1.in 1) node[anchor=east] {\scriptsize $b_2$};   
\draw (label_b1) -- (XOR1.in 2) node[below] {\scriptsize $b_1$}; 
\draw (XOR1.out) |-node{} (label_g1) ; 
\draw (label_b2) -- (label_g2) ; 

\node[ieeestd xor port, scale=0.75] (XOR2) at (0.5,-1.2) {};
\draw (label_b1) -|node[circ]{} (XOR2.in 1) node[anchor=east] {\scriptsize $b_1$};   
\draw (label_b0) -- (XOR2.in 2) node[below] {\scriptsize $b_0$}; 
\draw (XOR2.out) |-node{} (label_g0) ; 


\end{circuitikz}

\end{document}

this is the rendered output:

Answer 1

There are various issues here. If you look closely, the line from b₂ to g₂ is not horizontal --- the two nodes have different sizes and different base anchors, so when you draw the line to the node as opposed to the anchor, you get the border anchor nearest which is not correct. Moreover, the other connections are horizontal just by guessing coordinates...

I would do the following.

You want IEEE standard ports with 0.75 scale. State it in the preamble, that will assure consistency.

\ctikzset{logic ports=ieee, logic ports/scale=0.75}

Start with the top line (you can go the other way around, this is just my choice)

\path (-2,1.5) coordinate(label_b2) node[anchor=base east]{$b_2$};
\path (3,1.5) coordinate(label_g2) node[anchor=base west]{$g_2$};

to be sure to have the coordinates at the right point.

Then you place the first port, and if you want the label b₁ exactly 1.5 units below b₂, you can put the port using the anchor in 2 at a point with y coordinate 0 and connect it:

\node[xor port, anchor=in 2] (XOR1) at (0,0) {};
\draw (label_b2) -| node[circ](up dot){} (XOR1.in 1)
    node[anchor=east] {\scriptsize $b_2$};
\draw (up dot) -- (label_g2);

And now you have this:

if you want the vertical line to be more to the left, you can do it manually like this:

\node[xor port, anchor=in 2] (XOR1) at (0,0) {};
\draw (label_b2) --++(1,0) node[circ](up dot){} |- (XOR1.in 1) 
    node[above left] {\scriptsize $b_2$};
\draw (up dot) -- (label_g2);

...and the two labels b₁ and g₁:

\draw (XOR1.in 2) -- (XOR1.in 2 -| label_b2) node[anchor=base east]{$b_1$};
\draw (XOR1.out)  -- (XOR1.out -| label_g2) node[anchor=base west]{$g_1$};

The rest is similar. The complete MWE, without any magic number or strange coordinates, is:

\documentclass[border=10pt]{standalone}
\usepackage[T1]{fontenc}
\usepackage[siunitx, RPvoltages]{circuitikz}
\ctikzset{logic ports=ieee, logic ports/scale=0.75}
\tikzset{input text/.style={font=\scriptsize,
    above left, inner sep=2pt}}

\begin{document}
\begin{circuitikz}
    \path (-2,1.5) coordinate(label_b2) node[anchor=base east]{$b_2$};
    \path (3,1.5) coordinate(label_g2) node[anchor=base west]{$g_2$};

    \node[xor port, anchor=in 2] (XOR1) at (0,0) {};
    \draw (label_b2) --++(1,0) node[circ](up dot){} |- (XOR1.in 1)
        node[input text] {$b_2$};
    \draw (up dot) -- (label_g2);
    \draw (XOR1.in 2) node[input text] {$b_1$} -- (XOR1.in 2 -| label_b2)
        coordinate(label_b1) node[anchor=base east]{$b_1$};
    \draw (XOR1.out)  -- (XOR1.out -| label_g2) coordinate(label_g1)
        node[anchor=base west]{$g_1$};

    \node[xor port, anchor=in 2] (XOR2) at (0,-1.5) {};
    %% we do not over-draw here: start from the dot!
    \draw (label_b1-|up dot) node[circ](mid dot){} |- (XOR2.in 1)
        node[input text] {$b_1$};
    \draw (XOR2.in 2) node[input text]{$b_0$} -- (XOR2.in 2 -| label_b1)
        node[anchor=base east]{$b_0$};
    \draw (XOR2.out)  -- (XOR2.out -| label_g1) node[anchor=base west]{$g_0$};
\end{circuitikz}
\end{document}

I prefer to use simply east, west instead of base anchors for the lateral labels, but that's a matter of taste...