We carry lugs that fall into three of the four most commonly built types. These are all road oriented lugs, but hey, there aren't any lug police out there, so do what you want. Two of these types work with 1" steerer tubes and two work with 1-1/8" steerers. The terms: standard, oversized (OS), and double oversized refer to the tubing diameter that the lugs will accept. The larger the diameter the tube, the stiffer the tube, and the stiffer the tube, the stiffer the frame. In general if you're building for a cyclist of average build, you can safely go with 1" standard or OS. If the rider is taller and/or heavier, go with the 1" oversized, or 1-1/8" oversized. If the bike will be used for touring, oversized tubes might be a wise choice. 1-1/8" double oversized lugs go with even bigger tubes. We don't currently carry double oversized lugs.
In these illustrations the main triangle tubes are light blue and the lugs are darker blue. Each lug joins at least 2 tubes, with the BB shell accommodating 4 tubes: a downtube, seat tube, and 2 chainstays. The chainstay size further complicates matters with the BB shell accepting 22.2mm round chainstays or a variety of oval chainstays. Obviously you'll want to make sure that your chainstay diameter and shape matches with the chainstay socket portion of your BB shell.