Possibly they are... We need to check your SUBNET MASK in order to confirm.
If these computers also have a Subnet Mask of 255.0.0.0, then yes, your LAN and WIFI are on the same logical network - 10.x.x.x. (this may also be the case if one of your computers or interfaces has a different subnet mask)
If your Subnet Mask is 255.255.255.0, then they are not on the same network, they are on two different logical networks: 10.20.11.x and 10.255.255.x
The dropouts and crackles you hear may be an indication that your network buffer has been overrun... packets are either being dropped, or spending too long in the Network buffer to be delivered to your Audio Application on time.
From my own experience with Mac computers, it appears to me that OSX creates a separate data buffer for each logical network I create within my computer. This means that my DAW<>Slave network data is isolated from my DAW<><WIFI traffic (within my DAW). This is good - audio is clear and everything works very well.
If I put everything on one logical network, then it sounds like the traffic coming in over WIFI is causing my network data buffer to overrun. This is bad - sometimes a single instrument plays okay, but the more I load it up the worse the dropouts and crackles get.
OH, one other thought comes to mind... something else that can go wrong - your Ethernet ports might be set to Auto-Sense - meaning they will decide if they are going to run at Gigabit Ethernet, or 100b TX. This happened to me once because either cats or geckos, or cats chasing geckos in my studio. Upshot of it all was that my ethernet cable was damaged and one of my Macs kept changing it's mind about running at 1000Mbps or 100Mbps. That cause a lot of crackles and dropouts! I found it better to manually configure my Ethernet ports to 1000baseT and static addresses. That way it works or it doesn't. It's easier to figure out the cause of the problem this way.