I read in a comment on a different sentence that "rapid" is an adjective and "repede" is an adverb, why is it "rapid" here? Did I misunderstand something?
The person who said it wasn't clear. Rapid can be used as an adverb, but repede should be never used as an adjective.
You can use "repede" as adjective at least when referring to a river ("un râu repede de munte") ;-) I am not sure how to translate this in English?
When using the subjunctive to make a general statement, you need the second person singular conjugation: "Să hotărăști rapid nu este rău."
But I wouldn't say it's "more correct", this is one of the few instances in which using the infinitive is as natural as in English.