Which ever you decide, max it out at purchase, they are not upgradable.
Mac mini - Apple
M2 8 CPU...
Display Support:2 Displays*Resolution Support:6016x3384 (6K)*
Details:*This model supports "up to two displays" -- one "up to" 6016x3384 (6K) resolution at 60 Hz over Thunderbolt and one display with "up to" 5120x2880 (5K) resolution at 60 Hz over Thunderbolt or 3840x2160 (4K) resolution at 60 Hz over HDMI.
The Thunderbolt 4 ports support native DisplayPort output using USB-C as well as Thunderbolt 2, HDMI, DVI, and VGA output with adapters.
2nd Display Support:Dual/Mirroring*2nd Max. Resolution:5120x2880 (5K)*
Details:*Please refer to the earlier field for details, but if the primary display is 6016x3384 (6K) via Thunderbolt, the largest secondary display this system can support is 5120x2880 (5K), also via Thunderbolt. The HDMI port supports one display up to 4096x2160 (4K)https://everymac.com/systems/apple/mac-studio/specs/mac-studio-m2-ultra-24-core-cpu-76-core-gpu-2023-specs.html
M2 Pro 12 CPU...
Display Support:3 Displays*Resolution Support:6016x3384 (6K)*
Details:*This model supports "up to three displays" -- two displays up to 6016x3384 (6K) at 60 Hz over Thunderbolt and one display with up to 3840x2160 (4K) resolution at 60 Hz over HDMI.
Alternately, this model can support "up to two displays" -- one display with up to 6016x3384 (6K) resolution at 60 Hz over Thunderbolt and one external display with up to 3840x2160 (4K) resolution at 144 Hz over HDMI or one external display up to 7680x4320 (8K) at 60 Hz or 3840x2160 (4K) resolution at 240 Hz over HDMI.
The Thunderbolt 4 ports support native DisplayPort output using USB-C as well as Thunderbolt 2, HDMI, DVI, and VGA output with adapters.
https://everymac.com/systems/apple/mac_mini/specs/mac-mini-m2-pro-12-core-cpu-19-core-gpu-2023-specs.html
If budget allows perhaps a Mac Studio?
Mac Studio - Apple
https://everymac.com/systems/apple/mac-studio/mac-studio-faq/mac-studio-pros-and-cons.html
M2 Max 12 CPU..
Display Support:5 Displays*Resolution Support:6016x3384 (6K)*
Details:*This model supports "up to" five simultaneous displays -- four displays "up to" 6K resolution (6016x3384) at 60 Hz over Thunderbolt and one display "up to" 4K (4096x2160) at 60 Hz via HDMI or two displays "up to" 6K resolution (6016x3384) at 60 Hz over Thunderbolt and one display "up to" 8K resolution (7680x4320) at 60 Hz or "up to" 4K (4096x2160) resolution at "up to" 240 Hz over HDMI.
2nd Display Support:Dual/Mirroring*2nd Max. Resolution:6016x3384 (6K)*
Details:*Please refer to the earlier field for details, but if the first display is 6016x3384 (6K) via Thunderbolt, it can support as many as three more 6K displays via Thunderbolt and a fifth display as large as 4096x2160 (4K) via HDMI. Alternately, if the first display is 6016x3384 (6K) via Thunderbolt, it can support a second 6K display via Thunderbolt and a third display at 8K at 60 Hz or 4K up to 240 Hz over HDMI.
https://everymac.com/systems/apple/mac-studio/specs/mac-studio-m2-max-12-core-cpu-38-core-gpu-2023-specs.html
M2 Ultra 24 CPU..
Display Support:8 Displays*Resolution Support:7680x4320 (8K)*
Details:*Via Thunderbolt, this model supports "up to" eight simultaneous displays at 4096x2160 (4K) resolution at 60 Hz, "up to" six simultaneous displays at 6016x3384 (6K) resolution at 60 Hz, or "up to" three simultaneous displays at 7680x4320 (8K).
2nd Display Support:Dual/Mirroring*2nd Max. Resolution:7680x4320 (8K)*
Details:*Please refer to the earlier field for details, but if the first display is 7680x4320 (8K), this Mac Studio can support two more 8K displays. It alternately can support as many as eight 4K (4096x2160) displays total or six 6K (6016x3384) displays total.
https://everymac.com/systems/apple/mac-studio/specs/mac-studio-m2-ultra-24-core-cpu-76-core-gpu-2023-specs.html