If I want the experiment results data in my own time zone, do y'all recommend just changing the experiment queries to return dates in my timezone or some other way? e.g.

DATETIME(TIMESTAMP_MICROS(event_timestamp), 'America/Denver') AS timestamp

I would expect that by doing so, I could then set result query time boundaries in my own time vs UTC. Is this correct assumption?

I think

event_timestamp

in GA4 -> BQ sources is in UTC, so I think you may be right about your assumption here, but I'm genuinely unsure.