Just from experience, most processes in Acumatica should take less than 30 minutes, so spacing the schedules in that way should provide a decent level of assurance that there won’t be overlap. If something takes longer than that to run, you should reevaluate the server size for your instance.
But, that is all hypothetical, and you are correct, spacing the schedules is a passive solution. If you want a more concrete “Run B when A is complete,” you could possibly leverage the AUSchedule.LastRunDate or, if it’s triggering an Import Scenario, SYMappingActive.CompletedOn in a GI, filter for when “Import A completes Today,” then use that to trigger a Business Event that in turn drives Import B.
That’s a lot more moving parts and Business Events can get a little fussy if you throw too much at them, but it may work more like you expect.
Good luck!