LUG mount are like the std type mount where a large lug(x2) comes off and has a hole through it into which the bolt passes through to the hub lug onto which it is tightened.
RADIAL mount are holes at each end of the caliper but go from theoutside towards the centre, into the BRACKET, the bolts on the calipers run in the same plane as the pads, like a RADIAL engine with all the pistons pointing inwards towards the crank.
The bracket then has holes for these to bolt into, as well as some otyher holes at 90 degrees to these which are the normal hub mounting bolts.
There are many different AP calipers, but anyone doing the brackets would be able to supply the suitable ones.
There are far cheaper options for brakes as good as AP's as well.
tabetha