>>712905259
Milestone XP or just "get level ups as you go through the game". This takes away a lot of player choice and agency but prevents grinding and means players will always have roughly the power level you want for the area they are in.
Gold for XP is a tabletop concept where you just get XP equal to (or gold is equivelent to or is spent on upgrades) the XP you get out of an environment. If monsters grant little to no gold on their own creates and interesting dynamic where players are encouraged to avoid fights and may be allowed to extract whenever they want; encouraging risk/reward gameplay and greedy getting the better of them.
I'm not sure what you mean by "faction currency" but I quite liked games where advancing a faction questline or reputation with groups of various factions can grant upgrades; something like Bully where advancing in your classes grant upgrades, or getting unique tech trees only specific factions can grant to make playthroughs feel unique.
I also quite like some of the XP systems found in Fallout NV (even though that game also had standard XP) where you gained permanent bonuses for going down a checklist. I think having a system like this for a game, such as gaining advancements in the crafting skill only when you craft an item of a certain value or power level so you can't just spam lvl 1 iron daggers to grind to max level is a good alternative to traditional leveling.
Obviously in a perfect world you could make the XP totally divorced from the mechanics of the game and make it so just the player "getting better" is equal to the player getting more powerful in the narrative. This one is more arcade style or Roguelike style where it doesn't really count as leveling but maybe the platonic ideal of player/character advancement.