Yep, with the "As new backup files appear" the backup tape job will sit in "idle" state, waiting for new backup restore points to come. If the several jobs are selected as a source of backup to tape job, once the first restore point is created, the backup to tape job will start to transfer it to tape medias, while the other restore points will be placed in queue.
Whether the other restore points will be written to a current tape or to a new one depends on media set settings of corresponding media pool. If you want to write to one tape, till it's full, then, select "Always continue current mediaset" option.
As to usage of two different drives at the same time, you should create two different backup to tape jobs and point them to two different media pool (created per drive), as currently it's not possible to utilize simultaneously two different drives within one media pool.