Top 10 units for a STR team (in no particular order).
Captain Ability: 2X ATK & 2X RCV to STR units.
Special: DEX and QUICK orbs turn into STR orbs.
HP: 2488. ATK: 1252. RCV: 268.
Recovery boosts aren't recommended, but STR teams don't have too many options for captains, so a Recovery boost is better than no boost. Blamenco has decent stats and a special and should do better than Captains such as Gear 2 Luffy.
Captain Ability: 2X ATK and 2X HP to STR units.
Special: Surrounding orbs turn into STR orbs and deal 1000 fixed damage to all enemies.
HP: 2734. ATK: 1205. RCV: 262
Kuma really helps STR teams be tanky, his stats are good, and his special helps STR teams deal even more damage. Generally not as preferred over 2.5X captains, but Kuma is the best STR captain for now.