Laptop: What BIOS, Xen, Qubes, other(?) settings matter for battery life (w/o killing performance)?

BIOS: I know to disable SMT for security, regardless of the performance hit. My BIOS also has settings for Speed Step and Thermal Management - do these matter? Or once Xen takes over they become irrelevant? (At least, this is what I’ve read happens in the EFI world…)

Xen: The intel_pstate driver hasn’t been implemented in Xen 4.8; nor even in later versions, as I understand it. Therefore, the acpi_cpufreq driver applies. Using the ondemand governor, sampling rate and up threshold can be configured - does one matter more than the other? Is staying out of Turbo mode really important? I’ve read in more recent machines CPU frequency is less important than in the past - does that mean something else like maximizing high CC state time is more important? What about scheduling weights? dom0 by default is 2000 to other vm’s 1000 (except stub vm’s at 256) - has anyone played with any of these settings?

Qubes: Any point in the Linux tlp, etc. packages? I know some have used these in the past - have they made any real difference?

Appreciate any thoughts! Especially experience! Thanks.