Before flight, 14 CFR § 107.49 requires the remote pilot in command to confirm which of the following, in addition to assessing the operating environment?
Why: 14 CFR § 107.49(c) and (e) require the remote PIC to ensure control links between the ground control station and the aircraft are working properly, and that any attached or carried object is secure and does not adversely affect flight characteristics or controllability.
Part 107 has no requirement for a certificated repair station to test-fly the aircraft within 30 days; preflight checks are the remote PIC's own responsibility.
A visual observer is optional, not mandatory, under § 107.31(b) — the remote PIC and the person manipulating the controls may maintain VLOS without a VO.