What is the block / confirmation time for NXT coin? what is the block time to get my transaction confirmation? Do i still have to wait 10+ minutes to make sure a double spend didnt happen?
Transactions are being included into blocks in 1 minute in average. Longer you wait - higher a chance that a double-spending won't happen. There is no such a number that guarantees 100% irreversibility.

1 confirmation is not secure at all. 10 confirmations is recommended for small amounts, 720 confirmations - for big ones.