Extra camber "with coilovers" more comes from fact, that many of them have camber plates in set. But some of them don't. And one can purchase camber plates separately & use them with stock springs & struts (which actually are unadjustable coilovers). (there is also thing, that many aftermarket coilovers are intended for lowering, and with lowering one also naturally can gain some extra negative camber too).
But yes, many mention need for loads of negative camber for drift alignment, so at very least one should get camberbolts, but preferably compliment those with camberplates for much more camber. Or go for coilovers, limiting choice to ones with camberplates, but i'm not that sure that they are that much needed. Better spend that coilover budget on extra tire sets that will be quickly burned through / more seat time at track/training
.