I work mostly for print these days, and can’t advise you on the best normal/displacement workflow for your third party renderer, other than to mention it varies with the programs being used. Every tool does things a little differently.
As far as sculpting, though, something that trips people up when coming from a traditional modeler to Zbrush, is that those programs tend to use a normal smoothing effect to make even low polycounts look smooth. But that comes with a performance overhead (as well as an inaccurate view of the surface) that would be crippling to the kinds of polycounts Zbrush works with, which dwarfs the polygon potential of most other programs while still performing well even on modest hardware. So Zbrush doesnt do this…everything is real polygons. When working at low or medium res, you should expect to see some faceting. If you subdivide further that faceting will go away, but it is often useful to work at low or medium resolution, rather than high, because it is easier to sculpt form at that res. Dense meshes are resistant to easy changes in form, and work best for fine detail.
As far as learning curve, that’s true of any complex, major software tool. I picked up Zbrush in about a month of dedicated, focused study. I struggled for months learning XSI. You can’t study something halfheartedly and expect the best results. You have to dive in and focus, and set daily learning goals. I promise if you do this, after a month or so you’ll be much more comfortable.