Yes, Pokemon Let’s Go can be played in handheld mode. Playing the game in handheld mode makes it play completely different than playing with the Joy-Con controllers in docked mode. To play Pokemon Let’s Go in Handheld mode you will undock the Nintendo Switch and attach the Joy-Con controllers to the screen. You can then use the system as a handheld device.
Quick Answer: Yes
Playing Pokemon Let’s Go in handheld mode does remove the motion control aspects from the game. Instead of using the throwing motion with the Joy-Con or Poke Ball as you do in the docked mode you will instead use the face buttons on the controller to throw Poke Balls and catch Pokemon. During this part of the game, you can also aim at Pokemon during the mini-game by moving the position of the handheld to center the Pokemon on the screen.
Alongside handheld mode, you can play Pokemon Let’s Go docked with motion controls and undocked with motion controls as well. Unfortunately, the developers of the game chose not to include the option to play with anything other than the Poke Ball plus or the Joy-Cons when playing in docked mode. Using the buttons to throw Poke Balls is exclusive to the handheld undocked mode in Pokemon Let’s Go.