Nichrome wire temprature
Normally I'd do a technical search, but "urgent" so, ok...

https://en.wikipedia.org/wiki/Nichrome#Table_2:Current(A)_vs._temperature_characteristics,_straight_wire.

Table 2, one thing to note, if the nichrome is in contact with material you may want to go for a slightly higher temperature, because of heat conduction into surroundings- this can be a critical thing in an open air environment (wind cooling effects). Increase in resistance is small, so the 5V supply shouldn't have a problem at 5A if the wire is 26AWG or so, 24AWG may be getting close to the 5A limit once it heats up but if you're supply can really output 10A it would be the better choice as it has more thermal mass.