A good CCTV system answers three questions: what do you need to see, for how long do you need to keep the footage, and who needs to watch it remotely. Everything else follows from those answers.
Indoor cameras prioritize wide angles and clear faces. Outdoor cameras need weatherproof housings, infrared night vision, and resistance to backlight from headlights or the sun. For most offices, a mix of dome cameras inside and bullet cameras outside covers the practical scenarios.
NVR with IP cameras gives sharper footage and easier remote access than older DVR systems. Plan storage based on resolution and retention: a typical 8-camera setup at 4MP with 30 days of retention needs around 6 to 8 TB of disk.
Remote monitoring deserves more attention than it usually gets. Strong passwords, two-factor authentication, and a proper port-forwarding or VPN setup are what separate a useful system from a security risk.