Mac with Apple Silicon Chip (M1 or newer) because of secure ARM architecture. Newer chips have better security features, so it's best to stick with the most recent ones.
older devices (with T2 or T1 chips) are no longer recommended because they are vulnerable to checkm8, Passware Kit Forensic T2 Add-on and lack some hardware security features.
First steps
Distrust all networks by disallowing all incoming connections in Firewall settings (stealth mode).
Check for updates and enable automatic updates for OS and also App Store.
If multiple people use your Mac, limit the number of users with administrator privileges and set up a user account for each person, so that one person can’t modify the files needed by another
Backup with Time Machine and make sure you have encryption turned on.
Instead of using insecure, privacy-unfriendly adblocker browser extensions or programs, use the Reader mode in Safari.
If possible, use iCloud Private Relay. Alternatives are: Quad9 and Cloudflare. Quad9 provide an easy solution with Apple signed profiles. AdGuard and NextDNS are also options, but some users report problems like false positive filtering and stability/performance issues. Only Private Relay supports ODoH!
with Activity Monitor you can find Apps lacking the Sandbox and/ or Code injection Protection. Just enable the "Sandbox" and "Restricted" column. With the Terminal you can also check the Hardened Runtime.
Thunderbolt 4 cables enforces DMA protection using Directed I/O (Intel VT-d) technology that provides IO virtualization (often referred to as IO Memory Management Unit or IOMMU).
If Bluetooth accessories like keyboard or mouse is used, stay with official Apple ones as their firmware will automatically be updated by macOS and Apple's SoCs focus on minimizing attack surface by relegating security functions to dedicated hardware with limited functionality.