Yes refresh rate is a factor but running 5760x1080 at 144hz is a massive ask so unless you like tearing most of the time you would probably lock it to 60hz(fps) using v-sync in which case why go for the higher refresh rate monitor, it makes a lot of sense if you only have one because running 1080p at 144hz with your hardware should be quite realistic.
Hence the reason for suggesting the U2414's as they have a refresh rate which should be achievable, are quite a bit cheaper, have extremely thin bezels and are a higher quality IPS panel which are generally acknowledged to give better colour reproduction and at far greater viewing angles as well as nicer blacks. This comes generally at the price of refresh rate and response times although all things considered I think they make a good choice for triples. Mainly because I think the perceived quality of each frame will be superior with better colours and deeper blacks, the BenQ has some excellent features that would be of greater advantage if you only had one.
If you just wanted a single monitor though there are also a lot of new offerings to consider although i'm having trouble deciding myself after just watching Toms ROG swift review!
Just remember how quickly the amount of pixels increases with resolution, producing a 6mp frame 144 times a second is a monumental ask of even the most beastly graphics setup. Although ultimately I guess it depends what you want to play at what level of detail, check reviews for a pair of 780Ti's and see what FPS they achieve at various resolutions and go from there.
1080p = 2.1mp
1440p = 3.7mp
21:9 1440 = 5mp
3x 1080p =6.2mp
4k = 8.3mp
3x 1440p = 11.1mp
JR