The 737 autothrottle operates the same in both ALT HOLD and VNAV PATH by setting thrust to a value calculated to maintain speed in level flight and then slowly adjusting the target if not on speed. The autothrottle logic provides for more aggressive control of speed as the airplane approaches VMO or MMO.
In the Boeing wide body airplanes, VNAV does not respond as aggressively as the autopilot does in ALT HOLD