Cutting thin plywood with a diode laser is possible. You need air assist. If you are ok with about 24"x24"x3.5" work area, then the MPCNC is the right choice. If you want bigger, then the LR. But there is less info for lasers on the LR.
There really isn’t a good way to do CO2 on either. At least no one has made it easy. The MPCNC can get a little out of square and the laser can get away from it’s mirrors. Someone posted about putting the co2 laser along the gantry of a LR, but I haven’t heard anything in a long time.
If you need to cut through anything but the thinnest plywood, I think you need to get a CO2 laser. But you’ll be doing a lot of work to make it work on an MPCNC or a LowRider.