Alignment to verify plasmid from forward and reverse Sanger sequencing reads
Align all reads from a sample at the same time IMO. This will give you all of the information at once, and it should not be difficult. It should be very obvious whenever there's a disagreement between reads or between reads and reference.
I would also recommend inspecting chromatograms directly at all sites of interest (such disagreements, insertion sites, possible errors or mutations).