1. if you get an open headed drum, and it includes the lid, you can use the lid.
2. if you get an open headed drum and it does not have the lid, you can use a Weber lid or any other 22.5" lid.
3. if you get a closed headed drum, then you have to cut out the top of the drum, if you want to use a dome lid.
4. if you get a closed headed drum and you want a flat top drum, then you have to cut off the top while leaving at least an inch of the drum sides to flare out.
Norco's video shows him cutting out the top of the drum to allow for the use of a dome lid on a drum that was originally a closed headed drum. I would suggest you go figure out you needs first and proceed from there. I would say, use a dome lid, try and find an open top drum and see where you end up. There is never going to be a right way to get this done, the wrong way is gonna be to not get started. Like me.
By the way, closed headed drums are almost always cheaper, at least around here, than the open headed ones. Dome lids will give you more capacity than flat lids. UDS units are not any better based on how much thought is put into it, it is a low budget, recycled, shade tree unit that is best when built and used, not over-engineered and un-built. Unless you got a smoker already, go get you a drum and build something. Norco is a good guy to learn from.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."