You can use a combination of modular & the standard grid. Both have pros & con.
By using power of 2, you can easily scale your modular building block to get whole number.
If you make a wall panel of 64unit, You can easily scale it down to 32, 16, 8, 4 etc, & expend it to 128, 256, always a nice integer value, & can snap nicely. However if you use say 50units, when you half it, you get 12.5, a non integer value,half again, you get even worst, 6.25unit, & then 3.125 units…
I think you get my point.
However, to make leg of chair, or cabinet, there is no need to stick to power of 2, since they will not be scaled. a leg size of 3x3x60 will do fine.