Gecko G540 or?

[EddyCurrent]

I can imagine that if things are oversized they will use more energy to overcome their own inertia and losses than the energy used for light cutting. If this is the case I would expect the machine to be, 'not in control'.
A bit like trying to using a 50kg computer mouse for fast game playing.

[Ger21]

In my world its easy just to overdimension for example the steppers and the motors so that they should be able to cope with whatever i through at it.
.........................................Question is, are there any disadvantages doing light work with a muscular cnc

Adding larger motors can easily cause your machine to move slower, even though it may have twice the power at slower speeds.
Generally, the bigger the stepper, the slower it's capable of spinning.
Steppers are rated at their holding torque, when they are not spinning. The faster they spin, the less torque they have. With larger motors, the torque falls off more rapidly. If you gear them to spin slower, where they have more power, then you give up resolution.
I've seen cases where people have purchased large, inexpensive motors on Ebay. These motors are often too slow to get out of there own way. In most cases, these same people end up buying new, smaller motors. I've seen motors 1/4 the size make the machine 4-5x faster.

The best performing stepper motors will always be the smallest ones that meet your requirements. You should be choosing motors based on performance requirements.