You can only connect one ar2412 and 1 ar84 to the avantis.
If you need 40 channels on stage you have to replace the 2 ar84 for 1 ab168.
THe console runs native 96khz, the slink port has a sample rate conversion for the 48khz boxes.
If the second ar84 is near the desk for wireless, the avantis has 12 local in and 12 local out, so you don’t need them anymore.
https://www.allen-heath.com/media/SLinkConnections_V1_5_0.pdf
In this document is writen al the possible s-link connections, keep in mind that the avantis only has 1 slink port, there in no option card for a second slink, only for 96khz io boxes.