For sensing emotions, yes, it's a constant thing! It only works with face to face communication, though, so it wouldn't be an issue over the Network. Face to face, though, it's always active so brackets would really help!

With regards dreaming, Mirar is certainly detectable when he enters a mind. He's not always subtle. I would always plot that kind of thing out with you beforehand. The same would be true of dreamlinking! Zelos' permission would be required before the link could be established and if they don't give it, the link won't happen c: