We have different forks of 14nm process technology developed by different companies.
Samsung fork which is used by global foundries and by extension AMD- is the 14nm LPP, the series of that process timeline in strict samsung nomenclature is 14nm LPE - 14nm Lpp- 14nm Lpc?- 14nm LPU. (1st to 4th generation)
To confuse things AMD uses second gen 14nm LPP for its processors, but upgraded it to "3rd gen" for Rx 580, no one knows if that's their own revision of 14nm lpp or 3rd gen in strict samsung parlance (14nm Lpc? )
To confuse things even more glofo uses IBM designed 14nm HP SOI finfet for IBM server processors, this is a separate and completely different process to Samsung derived 14nm LPP, and is more suited to higher clocked/ higher power asics, more in line ( it still different) to Samsung's 4th gen 14nm LPU.
So when AMD uses the term 14nm+ on its roadmaps it could conceivably mean one of 5 things, 1) 14nm LPU 2)14nm LPC? 3) IBM 14nm HP. 4) AMD own revision of 14nm LPP. 5) AMD own revision of 14nm LPC.
As for performance I think 10-15℅ speed improvement with 14nmLPU and perhaps IBM14nm HP, less for 14nm LPC and AMD own revision of 14nm LPP/LPC
7nm IBM/glofo should be 25-30℅ faster than that in H2 2018/2019.
Just my thoughts, not sure about correct naming of 3rd gen 14nm LPC, just from memory.
Edited.
https://www.extremetech.com/extreme...ans-10nm-improvements-shows-off-7nm-euv-wafer