config = {
    opt1 = "etc..."
}
players = {}

function openMenu(playerName, configTable)
    players[playerName] = Something to get Table Key...

    -- read the table and create a gui not yet made
end

print(players[playerName])

"config"

function find(tbl, val)
    for k, v in pairs(tbl) do
        if v == val then return k end
    end
    return nil
end

table.find(t, value [,start_index]) -> [key or nil]