So are there examples of units that are best paired?
I'm really trying to wrap my head around this. It's complicated, and now I feel like I need to restart because I didn't do the things mentioned.
Yes many . One of the best example is Sumia, paired with Frederick. As single unit, Sumia might severely lacking during her introduction chapter because she's quite underleveled, while her stats are actually decent. She's just need little push to make her able stand on her own without too much babying. This is where Frederick come. Pairing him with Sumia will give extra DEF and STR, which make her quite versatile as she already capable of doubling some unit. Even in the long run, FrederickxSumia is one of the pair gameplay wise, since Frederick will gave bonus to two stats that Sumia quite lacking, DEF and STR.