@Cloyster and Conk stuff
I'll agree on the Cloyster because I've made a team focusing around him, using a core of Magnezone/Cloyster/Latios. I can't say anything about Conkeldurr, because I've never used him, and don't face him often, only thing I can really say about him is he's bulky af and can't be worn down by status reliably because people are scared of guts.
Cloyster is fantastic, but it sadly is vulnerable to the (arguably) two best types in the game- Fighting and Steel. He has a hard time getting past Scizor, Ferrothorn, and Skarmory, which pretty much means you have to run a reliable way to get rid of steels. Furthermore, he's weak to Terrakion and Keldeo- both Scarfed +Spe variants are faster than Cloyster even at +2. He's slower than Venusaur in sun, too- speaking of which, he's terrible against, considering all he can run is Rock Blast/Icicle Spear/Hydro Pump or Razor Shell, and Ice can be walled by Heatran and Rock gets walled by Grass types. Because of Fighting and Sun, I use Latios to counter. Cloyster also can't take a special hit for his life, and is weak to SR to boot.
So why use him after all that? Because he's unstoppable after he sets up. ScarfMons are pretty much the only thing that can beat him, and they need to have around base 108 in the first place to outspeed with a Scarf. His base Defense is excellent, so he could tank a physical hit if he needs to in order to set up. Even though Rock/Ice/Water coverage isn't that good against sun, you'll be hard-pressed to find a RainMon not named Keldeo that resists all three types. At +2 coming off a base 95 Attack, not much lives. With Skill Link, Icicle Spear and Rock Blast both always hit 5 times- giving Cloyster two base 125 moves with no drawbacks, besides Rock Blast's 90% accuracy. They even can hit through subs, and cause major chances to flinch if you feel like playing your luck with King's Rock. Cloyster definitely fits in at B-. It's not a huge threat every team needs to prepare for, but can definitely cause huge damage to any team lacking a Scarfed Fighting type, priority, or the Steel Types listed above. B- for sure.
On Cloyster's item, I understand why people use White Herb, but use Life Orb or King's Rock. Either way, Cloyster will never be able to take a Special hit. Don't waste the item.