6854 :
fa324 :
Of course it's just an estimation of time but it's pretty accurate if you download from steam and that is your maximum bandwidth.
The SSD question is more than legit.
Most games don't get much benefits from an SSD over an HHD except for loading time, arma (if i remember correctly) is an exception being an openworld
So will I see any in game benefits if I save it on my ssd?
As a general rule, games don't get any benefits from an SSD over an HDD.
However there are a few exceptions.
An SSD won't give you an higher frame rate (that's mainly your GPU job and marginally your CPU) but it can reduce loading time and stuttering.
In Arma 3, being a large sandbox, stuttering is due to the time your HDD/SSD needs to access textures/models and load them in your GPU's RAM.
SSDs have a much lower access time and higher transfer rate, giving them an advantage over HDDs to handle stuttering.
Long story short, if you have enough space in your SSD (120GB is not much actually) install Arma there, otherwise put it on your HHD as any other game and it won't change much.