Going back to the original question: 'What *should* a Warco Super Major Milling Machine be able to accomplish?'
Motor power and rigidity are the basic limitations. The Super Major's 1.5kW motor should be plenty in a small workshop.
Rigidity is a different issue. It depends partly on the design, mostly on adjustment. Rule of thumb, the heavier the better. Importantly, keeping gibs well adjusted and locking all the slides that shouldn't move during a cut. Work-holding to minimise unwanted movement is an art and a science! For example, the head and quill should be as close to the cut as possible, because it reduces leverage on the machine and it will bend.
My WM18 has a 1.1kW motor and weighs 220kg. A Super Major has 1.5kW, and weighs 450kg. That means a well-adjusted Super Major should be stiffer than a WM18. It doesn't mean the WM18 can't produce much the same output as a Super Major in terms of accuracy or finish. Rather the Super Major should be able to take heavier cuts, ie produce accurate work faster whilst requiring less TLC from the operator.
However, both machines demand careful setting up and work best with sharp tools on suitable materials. Light machines in this class are likely to chatter. Work-holding can be a major challenge – it's vital jobs can't move or bend whilst being cut. A Super Major won't be able to rip metal like a production machine; instead the operator is obliged to find the sweet spot at which it removes metal reasonably quickly whilst getting a good finish.
As milling machines go a 450kg Super Major is a lightweight. Many swear by the Bridgeport because it's a proven good performer just about small enough to be squeezed into a home workshop. It weighs about 900kg and has a 4kW motor. Jolly nice mill, and easier and quicker to use than a Super Major. But all things are relative: in the trade, Bridgeports are considered to be on the weedy side!
So a Bridgeport, Super Major and WM18 *should* all be capable of similar results, but don't expect a WM18 to be a Super Major or a Super Major to perform like a Bridgeport. The lighter hobby machines need more care and attention and work has to be done within their limitations. Life gets easier once a machines performance limits are understood. I often wish I had a Bridgeport, not because my WM18 can't do all I need, but because a bigger stiffer machine would make a lot of jobs more straightforward.
Woe is me. I haven't got space for a Bridgeport or a Super Major…

Dave