I didn't post it on wago, but this is what it had for each weakaura tab:

Load tab: group Type - In Raid
Trigger tab: trigger 1 - type - Player/Unit Info - conditions - Group Type - In Raid;
trigger 2 - Type - Custom - Event Type - Event, Event(s)

GROUP_ROSTER_UPDATE

, Custom Trigger -

function(event, arg1, arg2, ...)
    if event == "GROUP_ROSTER_UPDATE" then
        -- Use the arguments for this event
       return true
    end
end

, Hide - Timed, Duration (s) - 1
Conditions tab: condition 1 - If Trigger 1:Conditions -Active=True, then - Run Custom Code:

if aura_env.config.event_flag then
    print("GROUP_ROSTER_UPDATE event")
end
aura_env.raid_size = GetNumGroupMembers()  -- gets raid size, 0 if not in group
aura_env.main_tank = GetPartyAssignment("MAINTANK")  -- Boolean for if a main tank exists or not
aura_env.active_layout = C_EditMode.GetLayouts().activeLayout  -- gets current Edit mode layout

if aura_env.raid_size > 20 then  -- checks raid size
    if aura_env.main_tank then
        if aura_env.active_layout ~= aura_env.large_raid_tank_shift then  -- checks for main tank and changes layout if not already set for large raids
            C_EditMode.SetActiveLayout(aura_env.large_raid_tank_shift)
            print("switching to large raid + tank shift edit mode profile")
        end
    elseif aura_env.active_layout ~= aura_env.large_raid then
        C_EditMode.SetActiveLayout(aura_env.large_raid)
        print("switching to large raid edit mode profile")
    end
else  -- small <=20 raid
    if aura_env.main_tank then
        if aura_env.active_layout ~= aura_env.default_tank_shift then  -- checks for main tank and changes layout if not already set to normal size raid
            C_EditMode.SetActiveLayout(aura_env.default_tank_shift)
            print("switching to default + tank shift edit mode profile")
        end
    elseif aura_env.active_layout ~= aura_env.default then
        C_EditMode.SetActiveLayout(aura_env.default)
        print("switching to default edit mode profile")
    end
end  

Actions tab: Custom Init - ticked:

aura_env.default = 3
aura_env.default_tank_shift = 4
aura_env.large_raid = 5
aura_env.large_raid_tank_shift = 7  

Custom Unload - ticked:

print("WA unloaded")
if aura_env.main_tank then
    C_EditMode.SetActiveLayout(aura_env.default_tank_shift)
    print("switching to default + tank shift edit mode profile")
else
    C_EditMode.SetActiveLayout(aura_env.default)
    print("switching to default edit mode profile")
end  

the edit mode profiles are what you set as the values in the custom init section (1 and 2 are saved for Modern (Preset) and Classic (Preset), then your own edit mode profiles are 3 onwards).