Simculacrum isn't DM dependent. It states in the spell verbatim, "It obeys your spoken commands, moving and acting in accordance with your wishes and acting on your turn in combat."
Yes it is DM dependent. The spell creates a DMNPC that is (initially at least) friendly to you, and obeys your verbal commands (subject to its own interpretation of those commands).
Its a loyal soldier.
A DM has a little wiggle room to play its personality.
How can you say this? Its the DM plays it, who makes decisions for it (interpreting your orders through the filter of its perceptions) and who decides what the Sim wants. In a real campaign, I would likely play it as a copy of the Eldritch Knight, maybe with the twist that it wants to be a real person (the Pinnochio effect). It may even talk to the EK and beg him to help it. Depending on your relationship with the EK (and the campaign experiences of the EK to date), this could create an... intresting series of events.
It's basically like a summoned creature that will not act without its creators approval.
No its not. Its a part real/ part illusion copy of a creature. It has the same knowledge and shared experiences of that creature (spells prepared that morning, proficiencies, languages, experience level etc). It may even (if it is a simulacrum of the caster) also be aware that it is a simulacrum (or discover that fact later on). Depending on its knowledge of arcana and the actual spell used to create it, this could lead to all sorts of interesting interactiosn with it and the player.
The spell is very clear as to how the simulacrum acts.
"It obeys your spoken commands, moving and acting in accordance with your wishes and acting on your turn in combat."
So do loyal hirelings.
And compare this behavioural limit to Aasimovs laws of robotics for AI. Its nowhere near as comprehensive as those three laws, and Aasimovs get 'worked around' in fiction all the time.
So they tend to be a glass cannon to be used as soon as possible before the DM kills or dispels it.
And this knowledge (if possesed by the EK) is also possesed by the Simulacrum of the EK. Meaning it will know that you intend to use it as an expendable force multiplier (as you have done on earlier castings of the spell). It is loyal to you, and friendly to you, but assuming this knowledge is available to it, it may very well interpret your orders not exactly as you intended, and whn not given explicit orders to the contrary may decide that the best way to be friendly to you, or the best way to carry out your orders, is to do something very different to what you intended or asked.
My intent would be to make the Simulacrum spell almost as much trouble as it solves, and replete with RP and story implications to make casting it a real 'choice' by the caster instead of a gamist only force multiplier.
This isnt some kind of 'be a Jerk' move by the DM. Im just saying that messing with (self aware) AI is a dangerous and tricky proposition and it requires a raft of in game knowledge and variables for the DM to pull off, that will be too difficult in the parameters of the current test (for identical reasons why a
cohort would be difficult to adjudicate, and they would be reasonably common for PCs of this level as well).
In a normal campaign I would expect high level fighters to have cohorts/ leutenants and myrmidion/ mercenary armies, and wizards to have simulacrums/ constructs/ apprentices/ undead minions and rogues to have guild membership etc, but in the context of the current campaign these are all a little top difficult to adjudicate properly.