>>564000542+ abilities would be the healthiest option, since it allows for more differentiation between species (as well as logic issues like levitating without Levitate). The powerceep can be horizontal rather than vertical, and you should never have two abilities which do the same thing - Toucannon getting both Sheer Force and Skill Link is good, anything getting both Tough Claws and Iron Fist is bad (just give it a new attack-boosting ability instead).
2 items is the least healthy, since it's a significant vertical power boost with few restraints.
5 moves threatens to make everyones' movesets more similar to each other, unless it's done via items/abilities that add a specific new move.
You could go a middle ground between 2 abilities and 2 items by introducing "fighting styles" which can be swapped freely while out of battle. A Pokémon chooses its fighting style from a short list based on its species, though it typically includes some generic options like boosting STAB moves by +20%. If you want you could even tie it to Natures, with deliberately bad Natures (e.g. +Atk on an Alakazam) having a more powerful bonus.
