I really dislike that in mainline Pokémon games some Pokémon are straight up useless later in game. To ensure that every fully evolved Pokémon is useful up until the champion fight, most Pokémon got some sizable buffs to stats, moves or abilities. On the other hand some Pokémon (mostly legendaries) have received slight nerfs. Legendaries have, however, still the highest base stats. There is no way to perfectly balace hundreds of Pokémon but in Platinum Redux every Pokémon should be useful throughout the whole game. All stats, typings, abilities, learnsets and much more can be found in the documentation.

To ensure that no two Pokémon have the exact same purpose, there are no fully evolved monotype Pokémon in Platinum Redux. All fully evolved monotype Pokémon in Platinum received a regional form with an additional typing. Some dual types also received a type change. All Pokémon with changed typings have an adjusted color palette that indicates the type change. Around 50% of fully evolved Pokémon have regional forms so there will be a lot of surprises if you play blind. Every type combination is distributed at least once. It is very difficult for every Pokémon to have a niche if many Pokémon with the same (mono)typing exist; with these regional forms, every Pokémon is unique. Some of the regional forms are very obvious (Bug/Dragon Flygon), some are more unique (Dark/Psycho Absol) and some are very experimental (Gras/Water Venusaur; it is a toad right?). If you are just looking through the documentation and ask yourself how on earth Beautifly is a Bug/Ice type, remember that the sprites have different colors that reflect the type changes.