Intel and Nvidia graphics cards have too many limitations when it comes to low resolutions and dot clocks. I’ve been testing with am ATI Radeon HD5450 and it’s a great card for the money, unless you want any kind of 3D acceleration outside of retroarch. Any HD5xxx and HD4xxx series card should do, but your mileage may vary.
Some intel gpus play quite well at least with super resolutions, others not so much. A list would be quite useful to be honest.
As far as OS, hands down it’s linux. The best build I’ve found to work without issue is groovyarcade, though Ubuntu should do quite well too. It’d be amazing if Lakka could be recommended but it lacks x11 which CRT switching relies on for linux.
Windows will work but currently the linux code is much more current, it really needs to be worked on and ideally before 1.7.5 drops.