It’s less clear than that. The AI 300 series has RDNA 3.5 graphics, and they’re clocked a bit higher than the RDNA 3 graphics in the 7x40U series.
The AI 340 clearly loses to the 7640U. Four of the newer CUs simply can’t keep up with eight of the older ones. The AI 350 (8 x RDNA 3.5) and 7840U (11 x RDNA 3) trade blows in benchmarks. The AI HX 370 is in a class of its own with sixteen RDNA 3.5 CUs, but it’s also in a price class of its own.
All AMD APUs suffer badly with single channel memory; the performance hit on graphics is 30% or more. You always want dual channel unless you simply don’t care about performance.