Hard to give a definitive answer without more info about the team you're putting them on, the role you want each to play, whether it's single or doubles, etc. That said...
Orbeetle has decent Def and SpDef, and can make an effective Dual Screener. However, it suffers weaknesses to common STAB and coverage types (Fire, Flying, Dark) that will need to be compensated for elsewhere on the team.
Malamar is an effective disruptor. Abusing the Contrary ability can make moves like Superpower extremely devastating, and can cripple opposing setup Sweepers (Dragon Dance, Quiver Dance, etc) and setup Tanks (Cosmic Power, Calm Mind, etc) by reversing their stat mods through the move Topsy-Turvy. It's stats are pretty average all around, but it has actually rather good type defenses, taking 2x from Fairy and 4x from Bug.
Galarian Rapidash is more of a puzzle. Its stats are more like a Scout, but the only switching move it has access to is Baton Pass. It's Abilities are also pretty meh overall. Pastel Veil will likely see use on Wall/Stall teams in Doubles and Triples, because Toxic is the de-facto counter to them, and Pastel Veil prevents allies from being poisoned. This possibility is only increased by access to Heal Pulse. It has decent type defenses, as a Fairy/Psychic type. Like Gardevoir, it's able to cover the Poison weakness with Psychic STAB, and has access to Throat Chop for Ghosts, but lacks an option to deal with Steel types (Mystical Fire is special, while stats are physical -- Low Kick's damage is unreliable).