"A high-tech smartphone comparison thumbnail, 1080x1920 vertical aspect ratio. Three modern 5G smartphones arranged diagonally. Bold glowing text 'TOP 3 5G PHONES UNDER 20K' at the top. Technical icons for '12GB RAM' and '256GB' floating in the background. Cyberpunk aesthetic with neon blue and purple lighting, sharp focus, 8k resolution, professional tech review style."