How to swap side by side light switches
If the wires are long enough, just swapping the positions of the switches in the box will work just fine. The wires are all insulated, so there should be no danger if they cross / touch. Turn off the breaker before you do this work.

An alternative method would be to swap the switched-hots of the two switches. If you've got power coming in to your switch box (common nowadays given the requirement for a neutral in the box), this is probably a second black wire connected to the switch, but double check to be sure. On one switch it may be a red wire if the two switches control a light and fan in the same fixture, for instance. Again, turn off the breaker first.

For your 3-way switches, you'd swap the switched-hot and the traveler wires between the two switches.