This depends on your level of comfort with DIY. For lights I would change out the switches several options available for this. If you aren’t wanting to mess with electricity then changing light bulbs would be better. This also applies for cameras. Wired systems are always better than wireless for quality so if you ran network cables then I would look at a wired system. If not, just make sure you have good WiFi coverage throughout your house, possibly using a mesh WiFi or adding access points.