how much intuition do you expect to have retained? specifically, do you expect to have to learn type match ups and how stats work from roughly scratch?

supposing you don't have a strong feeling for which moves use the attack stat and which use the special attack stat, i would recommend Platinum as a good putting your feet back in. Emerald is also very beloved for good reasons.

to get aquainted with the modern series without straying to much from the OG game formula

in response to this, i offer a rough breakdown of the changing formulas across generations.

gens 1 - 5 have roughly the same feel: overhead view (with some partial exceptions in gen 5 games), sprite-based battles and animations, gimmicks are limited to new battle types.

gen 6&7: the 3ds era games, these switched to using 3d models for all the pokemon and the world, still a roughly bird's eye view of the world but without the strict movement grid to make use of the 3ds joysticks, and the introduction of battle gimmicks. gen 6 has mega evolutions which are an extra accessible evolution during a battle, somewhat divisive, but the most universally beloved gimmic. gen 7 still sort of had those but added in z-moves which were a once-a-battle overpowered attack.

gen 8&9: the switch era mainline games. behold, a conventional 3d camera view*. these started to experiment with less conventional battles. both of these generations completely excise mega evolutions and z-moves. gen 8 has "dynamaxing" which is a lot like mega evolutions but not limited to specific pokemon with a special hold item. gen 9 swapped the dynamaxxing during a battle for "terastallization" during a battle, which is swapping a pokemon's types for a different one, terms and conditions not withstanding. pokemon are on the overworld in both games. gen 9 has actual 3d movement in a meaningful way, gen 8 does not.

* well in the gen 8 games, there are routes like conventional games that have a fixed camera and there's a large open space called the wild area that has a conventional, 3rd person, player controllable camera. i personally found the wild area to be a very lazy and off-putting design.