When talking about this topic, I find it helpful to compare and contrast the difference in ethos between 4th Edition D&D and 5th Edition D&D.
In 4th Edition, generally each character's move speed was 6 squares, with the smaller races getting 5, and the odd ones (such as elves) getting 7. This is pretty comparable to 5e, where the ranges are all multiplied by 5ft, but otherwise remain the same.
Also worth mentioning is that in 4e, the ranges of most spells were 5 or 10 squares (compared to 30ft-120ft for 5e). Most ranged weapons were between 10-15 squares (vs. 30ft-100ft for bows/crossbows in 5e) and their long ranges were only double the base range (as compared to quadruple, in 5e). The charge action in 4e allowed you to move your speed and to make a melee basic attack, all as a standard action; what this meant was that a character with the typical speed of 6 could move 12 squares while still attacking on their turn. I would also point out that class features such as prime shot (for the Ranger and the Warlock classes) incentivized players to keep within about 10 squares of the center of the action.
What I observed from playing 3.5 and 4e in particular is that combat tended to involve crowding into whatever was the obvious open clearing in a given map (often near the middle.) Particularly with the flanking rules, there ended up being sort of a conga-line of melee characters and enemies all bunched up together. There wasn't a lot of "verticality" involved, most of the time, either.
This intention to keep the action close together is what inspired the more abstracted rules around positioning, in TNP. (Also, at a certain point, if you're far enough away, is it even fair to consider the combatants to be in the same "arena" as each other? Should they be in initiative against one another?) The system heavily borrows from 13th Age, where combat has effectively a front rank, a middle rank, and a back rank -- which TNP simplifies down to two ranks: essentially, melee and ranged (actually, "maelstrom" and "open").
The exception to this would be forms of "verticality" which in TNP have been either described as high ground (typically terrain or structures) or altitude (typically from flying or levitation). Cover also functions similarly to high ground, in that it is typically granted by terrain or architecture, and serves to bestow certain bonuses or penalties depending upon the relative positioning of the combatants involved; it's also possible to be behind the same piece of cover as an enemy, just as you can potentially be on the same piece of high ground with them.
When you are in melee with one or more enemies, this is called a maelstrom, and there are all sorts of rules around who can attack what, when in a maelstrom. This is also described as being adjacent; allies may join each other's existing maelstroms, and you can be adjacent to enemies or allies. If characters are in separate maelstroms from each other, they are not considered to be nearby; only allies who are in the same maelstrom together or who are open, are considered to be nearby. This is relevant for targeting with certain abilities. When you are in a maelstrom, you have disadvantage on ranged attack rolls, as is comparable to the rules in 5e.
You are not considered to be in a maelstrom anytime there are no enemies adjacent to you; this is referred to as being "open." As discussed in the previous post, some actions require you to be open, in order to take/trigger them. In TNP, making a melee attack when you are open is essentially the same as making a charge -- so there is no separate charge action; you close the distance with your target, and then attack it. Once you are adjacent to an enemy or enemies (i.e. in a maelstrom) your melee attacks can only target enemies in that maelstrom (until such time as you leave the maelstrom, of course.) Some classes can gain reach with their melee attacks, which allows them to target enemies outside of their maelstrom, as well as enemies which have some form of verticality.
The other "range" in terms of positioning (sort of, kind of) that I would include is being prone. Basically, since 4e functions off of a move action, it used this action to stand up from prone; since 5e functions off of move speed, it instead takes half of your speed to stand up. Moving while prone (i.e. crawling) essentially slows you to half-speed, in either edition. For TNP, since movement is so abstracted, I've settled on allowing any other normal movement while prone, but doing so will provoke opportunity attacks from adjacent enemies; this may need some testing to iron out. And obviously, you will need to stand up before you can attempt to climb or jump (which are the mundane methods for gaining high ground.)
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As always, let me know in the comments if there's anything glaring that I missed.
A bit of an extended break until the next post; check back for that on February 12th!