Optiminer itself does not currently have builtin controls for GPU fan, clocks or voltages. You can though use external controls to set those and they will be left unchanged by the miner.
The fgrlx driver works with a tool called 'atitweak'. You can download it from https://github.com/mjmvisser/adl3
Basic commands:
# Set fan speed to 80% for all cards:
atitweak -f 80
# Reset fan speed to default for all cards:
atitweak -d
# Set powertune +50% for card 1:
atitweak -A 1 -p 50
Use atitweak -h to print a list of all options.
TODO
The MSI afterburner allows control of various aspects of the GPUs for all AMD cards: https://www.msi.com/page/afterburner
The golden way for optimal performance are custom BIOS. This allows you to also change clock and voltage when running the miner under Linux. You can use Windows tools to download, change and upload modified card BIOS. As this is written to the card's flash the settings will be preserved between reboots and even when running under Linux.
TODO add links to tools