1) 2ms really is a 10-15ms monitor overall. 2ms is just the absolute lowest advertised specification for a certain g2g shade transition time (e.g., from 50 degree grey to 150 degree grey, whereas 255 degree pure white to 0 degree pure black and back to 255 degree pure white would take at least 15ms without any distortion artifacts). The difference between "5ms" and "6ms" is usually not noticeable, as far as the advertised specifications go for these such monitors.
2) Not really - the resolution difference shouldn't make the response times any different - these are completely separate measurements.
Still, a factory-advertised "6ms" monitor should be rather decent for most of the games. If you're really into competitive online fps shooters, then by all means go for 1ms - a serious gaming monitor. Gsync / freesync or at least ULMB (Ultra Low Monitor Blur) is the major feature that hardcore competitive fps gamers value the most of all (with at least 100-144Hz actual input refresh rate).
2) Not really - the resolution difference shouldn't make the response times any different - these are completely separate measurements.
Still, a factory-advertised "6ms" monitor should be rather decent for most of the games. If you're really into competitive online fps shooters, then by all means go for 1ms - a serious gaming monitor. Gsync / freesync or at least ULMB (Ultra Low Monitor Blur) is the major feature that hardcore competitive fps gamers value the most of all (with at least 100-144Hz actual input refresh rate).