Besides being more expensive, a fully enclosed helmet significantly reduces a soldier's awareness, making it difficult to see and hear, not to mention breathe! When not under heavy arrow fire, men-at-arms tended to keep their visors up for the same reason.

Likewise, leg armor is especially fatiguing due to the biomechanics of the human body. Weight carried on the limbs is felt more than weight carried on the trunk, and it's not surprising that dedicated infantrymen would opt to forego it. Indeed, we see troops of all kinds gradually abandoning leg armor in the 16th century, especially after torso armor became thicker and heavier due to the need to proof it against guns. By 1600, even heavy cavalry typically wore half or three-quarter armor.

Yes, they are accurate. Plenty of surviving armour around in armouries to show that the most common type of infantry armour in the 16th century was either half or 3/4 plate armour with open helmets.

The thing is, infantry wearing open helmets is the norm throughout history. Not only in Europe but everywhere else as well. The reason for this is breathing and awareness - one needs much more of both when on foot as opposed to horseback

When visors were invented this issue was mitigated and it allowed people to wear closed helmets on foot if they should wish to because they could open the visors when needed. But visoted helmets were expensive (the Howard accounts for example show a visored sallet costing almost 4x an unvisored one) so they mostly were used by men-at-arms/knights

Before the existence of visored helms the men-at-arms/knights solved the issue by wearing two helmets, a heavier closed great helm on top and a skullcap under, and would remove the great helms when needed. Such as when they fought on foot