What monitor should I buy to get 1440p HiDPI @60hz

So according to this guy: Re: MacBook Pro 13" mid 2014 at 60hz 1440p scaled with Dell P2715Q

Bottom line...
1- What monitor can we buy where we can set 2560x1440p HiDPI @60hz using our macbooks pros. ( I have a Mid2014)
2- Does it mean ALL 4k monitors... will look awful in macbooks ?

I bought the LG 27UD88, Im extremely disappointed, because the suggested 1920x1080 runs only at 30hz and honestly even tho it says HiDPI.. it doesnt look that good. I wish I could set 1440p HiDPI.. but no.. I had to download a freaking SwitchResX app to force 1440p @60hz LOW RES. that looks... meeeh.. feels like a downgrade for having a 4k monitor. Text looks horrendous.

So again,.. what monitor should I buy to get that 1440p HiDPI. and what size ?