The answer to the general question is yes - Macs have never required paired RAM although many machines get a 5 to 15% speed boost if you pair the RAM. In some integrated graphics applications on the 2007/2008 era designs, this could be larger a speedup for some graphics operations.
As long as your Mac doesn't exceed the total RAM the CPU/logic board wants to handle, you can split up the banks in any way you choose.
For your specific models, I would look at a reputable RAM seller like Ramjet to see if people have been reliably making more RAM work in your specific models. Often Apple will say the maximum RAM is 4 GB but 8 will work well if you have top of the line chips with the correct timing. Also - be aware that mixing speeds of RAM (1066 vs 1333) can be problematic or cause the system to fail to start up. Normally, permanent damage is not done to the memory or the computers when you place the wrong RAM in, but it can lead to aggravating crashes, video glitches and slowness.