you can't really have individual console server variables.
However, if you're using a system that relies on a console variable as a default, you can adjust by group using a multiplier or addition to the var for whatever effect/function/setting is getting applied.
Pseudo-Lua just to show logic
myvar = GetConVar(whatever_server_var) -- get the server var
mygroupinfo = {} -- set a table
mygroupinfo.admin = 1.02 -- add admin multiplier to the table
mygroupinfo.superadmin = 1.05 -- add superadmin multipler to the table
if ply:IsAdmin then -- are they admin?
ply:SetwhateverPlayerEffect( myvar * group.admin ) -- set whatever your wanting for that player to server variable times the admin multiplier
end
if ply:IsSuperAdmin then -- are they Superadmin?
ply:SetwhateverPlayerEffect( myvar * group.superadmin ) -- set whatever your wanting for that player to server variable times the superadmin multiplier
end