Is it safe to mix and match light bulb wattages and sizes in same fixture?
Yes, you certainly can use bulbs of different wattages in your fixture. The fact that one socket pulls more current is not important.
Bulb size is mostly a matter of light distribution and heat management. It's not relevant here as long as you don't have them up against something flammable or enclosed too tightly.
As you said, follow max wattage restrictions (though they're largely moot with modern LED bulbs).