While modern 4K TVs stretch the image, look for a device with a "4:3 aspect ratio" mode or scanline filters. Many DigitalArenaRetro platforms (like RetroArch) have shaders that simulate the glow of an old phosphorus screen.
A major concern for newcomers is the legal gray area of retro gaming. While as an idea is legal, the distribution of copyrighted ROMs is not always legal. However, there are legitimate ways to experience this world. digitalarenaretro