Blocks size and frequency issues


I read the block time will be 2.5 minutes and the size 2MB.
This means that in comparison to bitcoin block we have 8MB (4 times the freq and 2 times the size).
What are the consideration taken in zcash about latency issues that worried so much in bitcoin?
Is that because confidential txs are much bigger and as a consequence there will be less txs in a block? Even if there are less transaction, size and frequencies of blocks should give higher orphan rate...
Is the sighash quadratic complexity issue solved?