Given:
$x + 9 = z = y + 1$
and
$x + y < z + 5$
Step 1: Express $x$ and $y$ in terms of $z$.
From $x + 9 = z$, we have $x = z - 9$.
From $z = y + 1$, we have $y = z - 1$.
Step 2: Substitute into the inequality.
$x + y < z + 5$
$\Rightarrow (z - 9) + (z - 1) < z + 5$
$\Rightarrow 2z - 10 < z + 5$
$\Rightarrow z - 10 < 5$
$\Rightarrow z < 15$
Step 3: Determine the maximum possible integer value of $z$.
Since $z<15$, the maximum integer value for $z$ is $14$.
Step 4: Calculate the corresponding values for $x$ and $y$.
$x = z - 9 = 14 - 9 = 5$
$y = z - 1 = 14 - 1 = 13$
Step 5: Compute the required expression.
$2x + y = 2 \times 5 + 13 = 10 + 13 = \mathbf{23}$
Answer: (C): $23$