When I think about the concept of Low Fantasy, I think about a Conan-esque world.
Magic exists, but it is perverse, alien, and corrupts the minds and bodies of its users, therefore most arcane spellcasters fall into the evil, necromancer styled madman living in a stronghold away from everyone else who fears him and would kill him on sight, if they could. There aren't generally PC arcane spellcasters, but if there were, they'd be like Call of Cthulhu players being slowly driven mad and pushing toward an evil alignment with each spell cast as well as the time spent studying the subject matter. I think a witch would make a closer ideal low fantasy arcane caster, though more often as NPCs than PCs. Alchemists and bards might fit as well.
Divine magic might be less perverse, yet still corrupts the mind. However spells that completely heal you, remove permanent negative conditions, bring the dead back to life and allow planar travel would not function. There would be a heavy reliance on churches and clerical orders, heavy with politics, private agendas, obscure rituals and PCs unless missionaries would not be allowed to freely travel away from church control. I probably wouldn't allow clerics (maybe), perhaps inquisitors, oracles, and paladins would be a better fit.
Druids would exist, but the powers to shapechange to any animal might be curtailed somewhat - I would rather see something like a Celtic druid, and not so much as druid is defined in D&D.
Most existing magic items are ancient devices made when magic was more common (stuff you find as dungeon loot), so there would be no such thing as a magic shop, and creating magic items would be incredibly expensive, and a very rare to find a willing individual capable of making them for you, at any cost.
Most PCs are martial type characters - barbarians, cavaliers, fighters, monks, rangers, rogues and samurai, as most of the world is mundane.
Exotic monsters would exist, but they'd be rare, legendary, and probably not believed to exist by most people - I'm thinking werewolves, beast men, a limited number of giants and giant animals (snakes, like sons of Set), monsters of Greek myth like harpy, minotaur, satyr, hydra, etc. There might be dinosaurs in remote jungles or islands, and plieostocene fauna in the cold north. In Conan-esque games more often monsters are normal animals like bears, wolves, big cats, anacondas, giant monitor lizards. You would probably never see a dragon.
In Low Fantasy heroes can pursue and succeed at small victories, but their actions would probably not be world changing, nor world saving - more than likely everyone's goals are more petty and personal, and not offering social reforms, at best a full campaign might involve the destruction of an empire that would be as "big" as things get. Most often adventures provide some repuation, limited treasure, a way to get by, but not affecting the big picture. There would probably be more politics, instances of diplomacy and bullying, thus social interactions would have a far more pervasive existence, though hack and slash would still fit well. Ancient warrior empires and powerful city-states would be the limits to urbanization, barely governed homestead farmers would be far more wide spread, and barbarian tribes would dominate the wilderness beyond civilization - and the majority of real estate in the world.
General knowledge would be far more limiting and most people are illiterate, as education is only available to the aristocracy and even then it would be a very limited form of education.
This kind of world, would best fit my definition of Low Fantasy. There would otherwise be no need to emulate Earth, I don't see low fantasy as having to reside on the same world we live, though some define low fantasy as Earth related. It would be a mostly mundane world that is Earth like, but otherwise doesn't have to share the history and geography of our world.
