Winners:
Belial (WA4) vs. Shania (SH3)
Yuna (FFX) vs Fou Lu (BoF4)
Losers:
Simeon (Octopath) vs. Sephiroth (FF7)
HEAVY
Winners:
Worker 8 (FFT) vs. Lyon (Suiko5)
Reclaimer Dragon (WA4) vs. Nel Zelpher (SO3)
MIDDLE
Winners:
Roy (FE6) vs. Byleth (FE3H)
I think Roy is probably in trouble taken at lvl. 5 without giving him a lot of unrestricted Binding Blade charges. Taken at lvl. 9... Roy deals 0.44 PCHP to average defense (at lvl. 5, 0.42 PCHP). Byleth is listed at 1.11 PDur, so regens 0.22 "PDur" every round. Assuming no evasion (Roy is quite accurate) / crest procs, that means Roy wins in almost exactly (3*0.22 + 0.44 = 1.10) four rounds, five rounds at lvl. 5, and possibly still 5 rounds if being strict on that 0.01 missing. Taking time off for healing (if allowed) is damaging, though; that gives a free Renewal charge, so that's more like 5 rounds of offense + 1 round of healing = 6 rounds to win. But if the battle is going on that long, then the odds of Byleth getting a Crest of Flames proc for free healing dramatically go up, and Roy probably has to overuse the Binding Blade for however many charges he's allocated then (and gets in real trouble downgrading to a Silver Sword). So interestingly enough, Roy's healing game may not matter much, unless he's given 10+ charges unrestricted. He might just be YOLO attacking.
Can Byleth win in 4 turns? And who goes first? Roy is 6 move to a 6.6 average... Byleth is 6 move in EO, but the average is unclear. Move average is probably pushed downward by a wave of uncharacteristic 5-move DL Swordmasters for units that would usually be in higher move classes (SM Ferdinand rather than 8 move Paladin, SM Lysithea rather than 6 move Gremory, etc.). Roy is rather tanky, especially at lvl. 9, and the damage average in the 3H is sky-high. Silver Sword Windsweep is 0.24 PCHP damage (but gives up the ability to counterattack), Sublime Creator Sword WS is 0.26 PCHP and a healthy crit chance (but will break the SCS in no time flat), a Brave Sword or Sublime Heaven finisher is 0.39 PCHP, and a SCS regular attack double is 0.47 PCHP (but will eat a counterattack, at least assuming Roy hasn't broken the Binding Blade already). To maximize Renewal, Byleth really prefers the Windsweep options, no need to hurry up Roy's clock by inviting counterattacks. Level 9 Roy is 1.47 PDurability (Level 5 is 1.22 PDurability). So we're talking ~4 Windsweeps into a Finisher vs. lvl. 9, or ~3 Windsweeps into a finisher at lvl. 5.
Anyway, probably narrowly Byleth. If everything goes Roy's way (he's seen as barely exactly 4HKOing through Renewal rather than 5HKOing, no crests fire, no Byleth crits fire, Byleth uses the Silver Sword some to conserve SCS charges) he wins. However, despite Roy's good luck, Byleth has good luck too, and their crit chances are generally better, especially when using the Sublime Creator Sword. Byleth is also gambling on Crest of Flames activations. Seems like a little too much that can go wrong for Roy, but a very close match.
Losers:
Stocke (RH) vs. CHAMELEON MAN (WA3)
Considering Chameleon Man can't do anything, I would be inclined to let Stocke arrange a turn order that's just himself and not let Chameleon Man's "counter" kick in until the end of Stocke's chain. Obviously he loses otherwise, but I don't think a lot can interrupt RH "combos".
LIGHT
Winners:
Geela (TriStrat) vs. Locke (FF6)
Ryudo (G2) vs. Guile (CC)
Losers:
Sten (BoF2) vs. Natan (SH3)
Natan is reasonably tanky and Sten's resources are sharply limited, so think he runs out of gas?
Aika (SoA) vs. Zell Dincht (FF8)
Even if Zell is allowed to block Confuse, he has an uphill battle here... Aika can stall very easily, get to 25 SP, and finish Zell off that way.