Thanks for the reply, that makes perfect sense. Now I'm wondering if that monitor would give 60hz on a 2015 Macbook Pro with the integrated graphics card? I asked an apple rep and they said it wouldn't unless it has the Radeon graphics card in it but I've heard that the 2015 MBP without specifying if it has the extra graphics, can support a 4k monitor at 60hz with a DP to a mDP without issues. Is this correct? Maybe I should start a new thread for that one.
I have the lowest spec 2015 15" MBP and it runs a 27" Dell P2715Q 4k @ 60hz. The only hiccups I get are in Lightroom which has notoriously bad performance. Trying to edit photos at 5120 x 2880 has it understandably begging for mercy. A few of my friends run a 2015 15" MacBook pro with a large 4k monitor + a really ultra wide curved dell monitor at the same time and their machines are always breathing hard. Depending on the work you do I'd opt for a faster processor and gpu if you're really going to push it.
Thanks for your reply. Yes I heard that it can support 4k just as you are using it, and that it can tax the laptop at times, that's why I opted for not 4k but a 1440p monitor instead, to give it some breathing room.
A 4k monitor has 3840 pixels × 2160 lines so 8.3 Megapixels, a 1440p monitor has 3.7 Megapixels rounded up which less than half of a 4k monitor. I guess I'm answering my own question here but it sounds like it should work at 60hz it's just odd that the apple rep said it won't be able to run 60hz on a 1440p monitor. Does that make sense?
By the way he looked it up and referred to this spec sheet for the answer
https://support.apple.com/kb/SP719?viewlocale=en_US&locale=en_US
With at least the lower-end Dell tier of this monitor family, when used with this cable, it works well with the 2016. As the Dell display I use is 1080p, where as your tier is a 1440, I can't say for sure if you will get 60 Hz, but I don't see why you wouldn't.
IIRC there are also some USB-C-->DisplayPort cables designed for 4k & 60.