Not really. Although the examples also use the present subjunctive, the contextual implications are different.
Example 1:
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Vamos à festa quando eu decidir → With the verb in the future subjunctive, we understand you’re talking specifically about this one situation that is expected to happen at some uncertain point in the future. You’ll eventually go to this party whenever you say so. In this context, the first verb vamos works as a future form.
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Vamos à festa quando eu decido → With the verb in the simple present tense, it feels like you’re describing a general case or rule. It’s as if you were saying that you generally go to parties when you decide. In this context, the first verb vamos is understood to really be in the simple present.
Example 2:
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Vamos pedir a comida quando ele chegar (We’ll order the food when he arrives) → This sentence, with the future subjunctive, is also focused on this one specific future situation.
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Vamos pedir a comida quando ele chega → This sentence is actually incoherent. Vamos pedir, as an informal future structure, doesn’t match in terms of timeline with the present indicative chega. If you wanted to form a general sentence here, as discussed for the other example, you’d need to reword it to Pedimos a comida quando ele chega (i.e. all in the present tense).