Proof.
1 $\iff $ 2. This follows from the $\mathcal{I}$-goodness of $\varphi $ and $\psi $, see example 18.1.56.
1 $\iff $ 3. When $\varphi ,\psi \in \mathrm{PSH}_{\mathrm{tor}}(X,\theta )_{>0}$, this follows from proposition 21.13.58.
In general, fix an ample toric-invariant divisor $H$ on $X$ and a toric-invariant Hermitian metric $h_ H$ on $\mathcal{O}_ X(H)$ such that $\omega _ H\coloneqq \mathrm{dd}^{\mathrm{c}}h_ H$ is a Kähler form. We perturb $L$ to $L+m^{-1}H$ for $m\in \mathbb {Z}_{>0}$, then thanks to 21.11.47, we find that
\[ \Delta (\theta +m^{-1}\omega _ H,\varphi )\coloneqq m^{-1}\Delta (m\theta +\omega _ H,m\varphi )=\Delta (\theta ,\varphi )+m^{-1}\Delta \left(\mathcal{O}_ X(H)\right). \]
Then since $\varphi ,\psi \in \mathrm{PSH}_{\mathrm{tor}}(X,\theta +m^{-1}\omega _ H)_{>0}$, we know that $\varphi \preceq _ P \psi $ if and only if
\[ \Delta (\theta ,\varphi )+m^{-1}\Delta \left(\mathcal{O}_ X(H)\right)\subseteq \Delta (\theta ,\psi )+m^{-1}\Delta \left(\mathcal{O}_ X(H)\right) \]
for any $m\in \mathbb {Z}_{>0}$. The latter condition is equivalent to $\Delta (\theta ,\varphi )\subseteq \Delta (\theta ,\psi )$.
$\square$
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