[maxwmiller]

My bad, B8's are not available specifically for the E84. (edit): There is a B12 kit available for the 2WD X1's.

If you could find an adapter sleeve for the front knuckle, you could run the E9X B8's, which would cost you $870 new (as of 2/26/24 from ECS Tuning). This is actually cheaper than the B6's for the E84, which are currently $940 on ECS's website.

To answer your first question, I know a friend who had H&R on his E84 with stock shocks, but it was just a commuter and I don't think he ever pushed it hard. I'm not sure what you use the X1 for, but I wouldn't want to risk busting my shocks or even have a concern about it. Also for the price of lowering springs + the B4 kit, you could just buy BC racing coilovers, which I am leaning towards for my suspension refresh.