Option 1 -> Present tense used correctly in a time clause referring to a future event.
Option 2 -> Past perfect tense doesn't align with the future tense "will find" in the main clause.
Option 3 -> Simple past tense creates an illogical timeline with the future "will find."
Option 4 -> Future tense cannot be used in time clauses introduced by "once," "when," "after," etc.
Hence, Option 1: are settled -> In time clauses (with "once," "when," "after," "before"), we use present tense forms to refer to future events, not future tense. The sentence correctly uses present tense "are settled" in the subordinate clause with future tense "will find" in the main clause -> correct