A cleric isn't a village priest. A rogue isn't a common pickpocket. A wizard isn't a local scribe. A fighter shouldn't be a town guard of infantryman. Mundanity is for NPCs.
A previous edition - 3e? - had "NPC classes". PCs were Fighters, NPCs were Warriors; PC were Rogues, NPCs were Experts; PC were Clerics and Wizards, NPCs were Adepts. And so on. (Actually, that about covers it.) PCs were just straight up better than NPCs in the same "profession."
Anyway, on topic, "Group 1" are served by the Champion, and maybe the Battlemaster. "Group 2" are served by all the other subclasses that add a dash (or more) of supernatural. My daughter wanted to create a D&D character, but wanted
NO MAGIC (which included
anything fantastic, even most Barbarian rage) at all... her choices were actually
very limited! Champion, Battlemaster, Thief, Inquisitive, Mastermind, Berserker.
[that's not meant to be exhaustive, just descriptive, please don't bother correcting the list]
Group "1.5", your target audience, could - IMHO - be simply served reskinning Group 2 subclasses as greater and more fantastic/anime-ish levels of "skill". The warrior in my current campaign does this. He's a Battlemaster 3 / Arcane Trickster 5, but all his spells are flavored to be mundane (
color spray is a packet of powdered ghost pepper sprayed through the air;
minor illusion (used for ranged obscurity) is a ninja ghost-bomb egg), veteran skill (
silvery barbs is just an expert martial maneuver that manoeuvres himself out of danger or a foe into it at the last second), or the slow manifestation of Story-triggered "psionics" (
find familiar is just clairvoyance out to 100';
mage hand is telekinesis; even
booming blade is just his TK changing his sword into a vibroblade,
bladeward is a TK field that acts as a temporary shield). [The "psionics" are a stretch, but his backstory included an inherited (and ceremonially implanted) unknown device, so it served as a great catalyst.]
OR, slightly more effort - but laserllama already did it, as have many others INCLUDE WOTC (cough
4e cough) - have a selection of Battlemaster manoeuvres THAT GET BETTER at higher levels. Not just bigger numbers; the level 7 battlemaster should be able to do things the level 3 novice can't... not just 1pt more damage or AC. The level 17 battlemaster should be tripping godzilla, shifting the positions of every foe within 15', using enemies as shields against
fireballs and
dominates alike, and swatting both arrows and
firebolts out of the air with a flick of his weapon. Not just 2pts more damage or AC, and one guaranteed trick per fight.
I think those in "Group 1" would be okay with
their utterly mundane Champion or Battlemaster approaching Jason Statham or John Wick levels of martial capabilities, while those in "Group 1.5" happily step into Captain America-land and hurl a shield so it knocks a tank-turret out of alignment, bounces to KO three soldiers and disarm a fourth, then returns. Sorry, I meant "disrupts a spellcaster's spell, kills three minion warriors, grants a contested Athletics check on a fourth, then returns". That first bit could be a hit that forces a concentration check like an improved Mageslayer feat, or a reskinned
counterspell magical effect, or a unique new maneuver that... I don't know... allows the Fighter to change the caster's targets or maybe cause a Wild Surge.
Just cater to everyone's tastes by maybe having a [tag] (or three) so the "my fighter is mundane" (Group 1) folks can filter things to whatever level of believability they are okay with. Their level 1-7 experience isn't disrupted, because they know their level 20 abilities are still "explainable" in a mortal way. Group 1.5 has more choices, which perhaps are less numbers-y and more epicly versatile... perhaps straying into wuxia-land and anime for the last 5-10 levels. And Group 2 is still fine - they took Eldritch Knight or multiclassed anyway, no worries.