TDeck has more features like keyboard, more IO options built in and bit larger RAM (I believe)

Tbeam is same without keyboard (great device)

RAK also has some great dwvices

Simplest is to just get started with a simple Heltec V3 or LilyGo T-Beam (SX1262/SX1276) as the T-Beam comes with a place for standard 18650 battery


Checkout more hardware options with details here👇
https://meshtastic.org/docs/hardware/devices