Loco Questions

[Omogoto]

Hello I just have a few basic Loco questions because I have no RL railroad knowledge.
#1 When you use 2 engines does it matter if they are end to end?, tail to tail?, or just in line same direction on both? and why?
#2 On all loco's I noticed they is no start/stop, or on/off, when not in use they all just sit there running at idol. Are they consuming fuel all this time?
#3 When using AI I noticed my driver sometimes does not follow speed limits, and once he slows down for say a 15 mph yard limit once past he does speed back up, and sometimes he blows through a yard limit at full speed. Also when you assign a speed, say 45 the loco will not go this speed, I do know the entire map has speed limits, and it seems like, sometimes the AI is pretty good at managing this, and other times not so much. Is there a "best practice speed to set an AI train?
#4 I do have crews assigned to all my Loco's but is is unclear why, is there any use or benefit to using Loco train crews?
Whats hard for me sometimes is knowing what in this game is intended and what is not yet refined due to its "early access" status.
Thanks all

[🚂🚃Taschi🚃🚃]

#1 - on steam engines, it is generally preferable to have all engines run boiler-first because they tend to run smoother that way. On low-speed routes like the one in the game, it doesn't matter that much. When I run GP7 diesels in pairs, I want them to be end-to-end, so that there's a cab in front no matter which way they run, but that's not a 100% requirement - they can run with the long hood in front (and some railways preferred to run them like that in the early days, but the ones in game are set up for running primarily short-hood in front).
#2 - no, no fuel consumption while idle in the game.
#3 - it seems like some yards don't have the yard limit properly programmed in, i've noticed this in Robinson Gap, for example. Most of the route has line speeds of 30 to 35mph but there are a few 45mph sections and the AI will go to 45 in those sections.
#4 - assigning crews is just to keep track who is responsible for which rolling stock and which tasks in multiplayer sessions. It's safe to ignore in single player. (I've seen people claim that the AI will derail trains when you don't assign them to a crew, and stuff like that, but I believe that is nonsense.)

[bfcmik]

In single player the main use for having a crew is so you create switch lists. These are a good, quick way to see what needs moving where if you tag every wagon when it enters your interchange.

[Omogoto]

Great replies and thank you both.