I'll be honest I haven't tried different displays other than what the given system required. This what I can tell you/
The Late 14/Mid15 systems use a LG display: LM270QQ1 (SD)(A1) or LM270QQ1 (SD)(A2)
The Late15 system uses a slightly different LG display: LM270QQ1 (SD)(B1)
The 2017 system uses still a different LG display: LM270QQ1 (SD)(C1)
These displays are hard to find as people still prefer the 27" system and theres been a bit of an issue with the 24" displays messing up with dim bars!