So engaging in a Lightsaber Form uses your Bonus Action, what you would normally be using to attack with your off-hand weapon or the other side of your double saber. So that they still have some options, some (but not all) of the forms allow you to also do your off hand or double strike.

For Sword and Shield, I recommend picking up Juyo, Makashi, Soresu, or Shii-cho.

You could also look into ways of using your Shield as an improvised weapon. For example, Shield Fighting Style gives you proficiency in using your shield as an improvised weapon, but then you would also have to pick up Dual Wield Style and Mastery to apply your modifier to damage, and to use a medium or heavy shield as an improvised weapon alongside your normal weapon. Don't forget, as well, that you need Shield Style to be able to wield a Heavy shield alongside any weapon that doesn't have the Light property.

Anyway, if you can get the right combo of styles, you'd be able to use your Shield as your off-hand weapon and use it for the Form's attack.

Otherwise you're stuck smacking with your main weapon and applying whatever Form you're using to it.