Kaivalyaarthis are those who desire Jivatma anubhavam after their life ends. There is a separate world for them. They will reach that world and experience the Jivatma . But even that world will be destroyed during pralayam (dissolution).
Mumukshus are those who desire Paramatma anubhavam. They attain Moksha and reach Sri Vaikuntham. There they attain the supreme bliss of enjoying Perumal (Bhagavad anubaham) and will be with eternal happiness.