Yes, you can enable it. Also enable powerd in pfSense to take advantage of it. I run that here and haven't seen any significant performance issues:
[24.08-DEVELOPMENT][admin@5100.stevew.lan]/root: sysctl dev.cpu | grep freq dev.cpu.3.freq_levels: 2200/0 2100/0 2000/0 1900/0 1800/0 1700/0 1600/0 1500/0 1400/0 1300/0 1200/0 1100/0 1000/0 900/0 800/0 dev.cpu.3.freq: 1400 dev.cpu.2.freq_levels: 2200/0 2100/0 2000/0 1900/0 1800/0 1700/0 1600/0 1500/0 1400/0 1300/0 1200/0 1100/0 1000/0 900/0 800/0 dev.cpu.2.freq: 1400 dev.cpu.1.freq_levels: 2200/0 2100/0 2000/0 1900/0 1800/0 1700/0 1600/0 1500/0 1400/0 1300/0 1200/0 1100/0 1000/0 900/0 800/0 dev.cpu.1.freq: 1400 dev.cpu.0.freq_levels: 2200/0 2100/0 2000/0 1900/0 1800/0 1700/0 1600/0 1500/0 1400/0 1300/0 1200/0 1100/0 1000/0 900/0 800/0 dev.cpu.0.freq: 1400Steve