Just simply, PoW/PoS diff adjusting should be  separated at least as an operand.
Anyway, there is no answer, longer block time is better than shorter
But, it makes an delay of transaction.
Anyway, the block time of this coin is not a big problem when check over the time.
The most problem is interference of diff between PoS and PoW.
Anyway, if the network hash rate is bigger than 200M, this coin will be stable.
But, just 50-100Mh now,