What are the differences between the normal, hard and 'True West' difficulty modes?

I know, the question is more than 3 years old, but in case someone wants to know, here is what i found out after searching the internet with no success and testing it myself:

• the enemy count stays the same
• normal enemies stay at the same hit points, except bosses, which get significantly more (i would guess hard: 50% more, true west: 100% - 150%)
• the higher the difficulty level, the more do enemies stay behind their cover, apart from that i couldnt observe different ai behavior
• i guess the enemy is dealing 50% more damage on hard and on true west what feels like 100% or even 150% more damage, in addition their shots are much more precise on hard and true west, but i cant say exactly how much
• the new game+ feels exactly the same, no changes in difficulty
• as you said, in true west mode the hud, crosshair and hints get removed

I hope this helps