yet couldnt get what I thought or what WTM estimated!
WTM is never very accurate. My experience, they can be off by as much as 30 percent.
When I look through, blocks are rare to be found on suprnova, whereas pools with minimal hashrate could find considerably. Why is that?
This is simply not possible. The higher hash rate wins consistently. That's why people choose suprnova and similar large pools, because their rewards are consistent. A minimal hashrate pool can "only appear" to be winning for a very short period of time (because of pure luck).