Brycen
Simisear (39): charcoal Fire blast OHKO's everything. If you're worried about missing, you can set up a sunny day or work up on Vanillish which turns Flame burst into a a OHKO on everything. great matchup
Seismitoad (38): muddy water barely fails to OHKO Vanillish after a rain dance (mystic water guarantees the OHKO). It's a 2HKO on Beartic, but Beartic always uses swagger. Seismitoad can survive one round of hitting itself and getting hit by icicle crash, but then you need to heal if you also want to beat Cryogonal. A more reliable way of soloing the fight is with a persim berry. Brick break 2HKO's Beartic after a swagger and Cryogonal is outsped (only in rain) and OHKO'd. Good matchup, but you do need a persim berry to make it reliable.
Archeops (39): Rock slide OHKO's everything. Expert belt is required though. Great matchup
Ferroseed (38): gyro ball depletes about half of Vanillish' health bar, even after an acid armour. Vanillish then usually starts spamming frost breath instead of acid armour, so you can set up two curses. Gyro ball then OHKO's. Beartic uses swagger again. If you hit yourself in confusion, you need to heal the turn after. If you don't hit yourself, you OHKO. Cryogonal doesn't do much damage and is also OHKO'd by gyro ball. I also tested Ferrothorn. The matchup plays out mostly the same, but it's more reliable since you can use persim berry over eviolite. Overall, great matchup, but it's a bit luck based for Ferroseed.
Stunfisk (38): with a magnet equiped, discharge is a 2HKO on Vanillish. Thunderbolt also 2HKO's without magnet, but that requires a backtrack and discharge is generally better anway. If you get the paralyze on discharge, Stunfisk can beat Vanillish totally unscathed since Vanillish alsways uses acid armour on turn one. Beartic is 2HKO by rock slide after a swagger. Stunfisk can comfortably tank an icicle crash as well, so with a persim berry you can actually beat Beartic fairly reliably. Sometimes it goes for swagger twice in a row though, which makes the matchup luck-based. Cryogonals aurora beam doesn't actually do all that much damage (it's a 4HKO), so you can tank it and OHKO with a +2 rock slide. Overall, the matchup isn't all that bad really, for a slow pokemon with an ice weakness anyway.
Drayden
Simisear (42): If you carried yawn all throughout the game (I did), you can set up here because Fraxure ALWAYS uses at least two dragon dances. You can generally set up three work ups, which is more than enough to OHKO Fraxure with return. However, it's a range on Druddigon and Haxorus. Sometimes you can set up four work ups which guarantees the OHKO on both, but this is inconsistent. Then again, Simisear is just bulky enough to survive a dragon tail even at +3, so if you deposit the rest of your team, you should be able to get 4 work ups and sweep. I also tried a different strategy that gets the kill on Druddigon as well with just three turns of setup, but you have to give up on flame burst for it. Basically, instead of using work up three times, you use work up twice and sunny day once. After this, charchoal fire blast OHKO's both Fraxure and Druddigon reliably, but it's still a range on Haxorus. You also have the option of will-o-wisp, which is very useful here. Overall, it's actually a really good matchup, but you do need to be a bit overleveled if you want to solo it. I actually tested this as well. At level 44, the three work ups + silk scarf return becomes reliable.
Seismitoad (41): bulldoze is a 3HKO on Fraxure. You beat it without taking damage reliably, even considering both of Drayden's healing items, since Fraxure never stops spamming dragon dance. Druddigon and Haxorus are both 4HKO'd. Druddigon usually just phases you out with dragon tail, after which you have to heal. Seismitoad can then come in on Haxorus again at full health. Haxorus generally uses two dragon dances, so you should bulldoze to negate the speed boost. If Haxorus attacks (read: does not use dragon dance) and you use bulldoze again, you can outspeed the next turn. If you made Drayden use up his potions on Fraxure, you can actually beat Haxorus too. Overall, the matchup is alright, but not amazing. You also need some healing
Archeops (42): Acrobatics OHKO's Fraxure. Druddigon survives an acrobatics easily and puts Archeops dangerously close to defeatist range. If you use dragon breath, which doesn't trigger rough skin, you can barely avoid getting knocked into defeatist range and follow up with an Acrobatics for the kill. Rough skin will then put you in defeatist range anyway, so you have to switch and heal. Haxorus isn't OHKO'd by acrobatics, but you can get the 2HKO even if Haxorus puts you into defeatist range so it doesn't matter much. Overall, decent matchup, but Druddigon poses some problems mainly because of rough skin.
Ferrothorn (41): Fraxure uses dragon dance twice again, so you can 2HKO it with gyro ball without taking damage. Druddigon can't touch you if you just curse up. Even revenge won't do much damage. Eventually it will phase you out with dragon tail, but you can just immediately come back in because Druddigon really can't do much to Ferrothorn. Haxorus can't touch it either and is OHKO'd by gyro ball after some curses. Overall, amazing matchup. It's the most relible if you deposit the rest of your team, but it's not really necessary.
Stunfisk (40): Fraxure is barely 2HKO'd by soft sand mud bomb. Druddigon is 4HKO'd, but none of it's moves are all that threatning to Stunfisk so you can win by just spamming mud bomb. Drayden will heal, so you have to heal too. You also probably need an ether for mud bomb. Haxorus is 4HKO'd, but it comes close to a 3HKO. Mud bomb accuracy drops and static will likely come into play in this matchup, which is a huge help to Stunfisks survivability. Overall, pretty good matchup. With some healing support, you can actually duel all three of Drayden's pokemon well as nothing Drayden can throw at you is very threatning to Stunfisk.
And now some suggestions for Ryota's next run. I recommend Audino as well, because it is very fun to use and it also helps against Lenora a lot. If you want another early pokemon, I recommend Blitzle since not a lot of people have used it other than myself. I think it's decent actually, but it falls off hard in the late game. If you want a bit of a challenge, I recommend Patrat. It is absolute garbage until it evolves, but when it does, it's actually quite good for a while. It has a great movepool which makes it surpisingly good in the mid-game matchups.