Just like you, I adore Shadowheart and Lae'zel as love interest and started to also like Minthara. Too bad she has too little content compared to the rest. As for npcs, I absolutely love Isobel and Aylin, even on my evil playthrough I couldn't force myself to hurt either of them.
For Shadowheart I specifically prefer to play as a Selunite, love their dynamic, bickering back and forth till act 3.
I'll be honest, I'm not really impressed by male companions or npcs. Halsin, Astarion and Emperor are top 3 characters I just can't stand, at all.