For your lighting control system, it would be expensive but possible to make every fixture independent. Group the light fixtures as it makes sense. Each independent fixture or group will be wired to a remotely mounted dimmer or switch. Some systems have multiple dimmers and switches in a single device called a module. The systems can be programmed to operate as you suggest with group A, B etc., controlled by individual buttons or by current use of the room which is actually easier to deal with in large rooms with lots of zones of light to manage. Button 1 is for reading, 2 is for TV, 3 for movie, etc. A combination of these two button designs can be most effective.
Wall washing (what you had) is a bit different than more intensely focused accent lighting which is what normally one thinks of when displaying paintings in a home. Narrow hallways full of small family photos could be a good use of wall washing. Galleries that tend to change paintings often might flood an entire wall but some galleries move their more precise accent lighting at every show. Halogen is a popular lamp choice. For smaller fixtures and precise beam control use MR16 lamps. Par 30 lamps are lower cost per fixture. The size and placement of paintings would be helpful to know for whomever is laying out the lights.
Step lights add more visual drama. I’m not convinced that they add any safety unless if in the riser they are in each one. Anything else is just for effect. If in the side wall then you have to know what fixture you are working with.