Hello! Bug Catcher Burn here. I'll do as much as I can for this team. For the mega I'd go with Mawile, because I think she is the best of these megas.
Charizard:
Non-mega Charizard is not too great. So, replace it. My personal favorite Fire-type to replace is Infernape. It is better to have a Fire replace than Dragon because you already have another Dragon in Dragonite. For a set, I have 3; physical, special, and mixed.
Infernape@ Life Orb
EV's: 252 SA/252 Sp/4 HP
Ability: Blaze
Modest Nature
-Flamethrower/Fire Blast/Overheat
-Focus Blast
-Grass Knot
-Nasty Plot
This is the special set. Nasty Plot boosts his already decent special attack to great levels. Flamethrower and Fire Blast and Overheat are Fire STABs, depending on your personal preferences. I like Flamethrower the best, but you need to decide. Focus Blast round out the dual STAB. Grass Knot is honestly filler because it is the only competitively viable coverage move he learns besides Hidden Power.
Infernape@ Assault Vest/Life Orb
EV's: 252 Ak/252 Sp/4 HP
Ability: Blaze
Adamant Nature
-Blaze Kick/Flare Biltz
-Close Combat/Mach Punch
-Earthquake/U-Turn
-U-Turn/Swords Dance
For the physical set, Nape has much better coverage options. Blaze Kick or Flare Blitz come down to Power or Health (recoil). Close Combat and Mach Punch again is Power or Priority. EQ and U-Turn is just preference, as is Swords Dance or U-Turn. Use LO if SD, AV if not.
Infernape@ Assault Vest
EV's: 252 Sp/ 128 Ak/ 128 SA
Ability: Blaze
Naive Nature
-Flamethrower
-Close Combat
-Grass Knot
-Earthquake/U-Turn/Stone Edge/Shadow Claw/Poison Jab/ThunderPunch/Whatever
Mixed Infernape is my favorite. You know the deal for Flamethrower and Close Combat, as well as Grass Knot. As for all those, three words: Coverage. Your choice. Naive over Hasty because you'll get some Special Defense back with your Assault Vest.
Mega Mawile:
Replace Fire Fang for STAB Iron Head. Sucker Punch is also better than Stealth Rock.
Sylveon:
Half these moves are not very good. Make the set the following, changes in Bold.
Sylveon@Leftovers
EV's: 252 SD/252 HP/4 SA
Ability: Cute Charm
Calm Nature
-Moonblast
-Toxic
-Wish
-Heal Bell
Basic Stall/Cleric Sylveon.
Aegislash:
You need King's Shield on here to revert to Shield Forme. Replace one of your Ghost STABs.
Swords Dance may also be needed.
Ampharos:
Replace for Jolteon, as its non-mega is outclassed:
Jolteon@ Air Balloon
EV's: 252 SA/252 Sp/4 HP
Ability: Volt Abosrb
Timid Nature
-Thunderbolt
-Volt Switch
-Signal Beam
-Shadow Ball/Hidden Power Ice
Basic. No need to explain, plus I'm getting kinda tired.
Dragonite:
Replace Hurricane for Roost, so you can return to Multiscale range. Make the spread and Nature: Adamant/ 252 Ak, 252 Sp, 4 HP.
There you go! Hope I helped!
-Bug Catcher Burn
