In my current playthrough, I've only used two of these: Kricketot and Combee. As for Kricketot, I only really used it for a bit until I could build my full team up to what I wanted. However, I've heard it does have a fair bit of use early game with Technician + Fury Cutter. Combee... <3 The gender disparity was rigged against me with only a 12.5% chance to find a female. However, one Cute Charm male Igglybuff later, I had a suitable female Combee in short order. Once evolved into Vespiquen, it is actually a pretty powerful early game Pokémon, with nice stats though the move pool isn't great without TMs and her good moves won't really come in until level 25.
Kricketot is indeed available freely via event in Peridot. Combee is available as a headbutt Pokémon from the Opal Ward outside of the Grand Hall.