One of the first things a DM should do before running a sandbox campaign is to decide on their demographics of their world and answer those sorts of questions.
I do find this is quite important to setting the feel of the setting. Eg Primeval Thule has a 'badass planet' vibe where the typical Legionary is 52 hp CR 2 and there are Lomari squadrons of guys with over 100 hp each. Very different from a setting where the 11 hp CR 1/8 Guard represents a skilled professional soldier.
Personally I'd peg the standard 5e Goblin & Orc stat blocks as humanoid equivalents of the NPC Tribal Warrior, rather than Commoner, and the Hobgoblin with its 75gp chainmail armour a step above that. Or maybe hobgoblins are Spartans. But I definitely will use stronger variants; eg I tend to use the Orog stat block for elite orcs, swapping out Plate for Splint or Chain.
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