Thanks Dan B. Great suggestions. Exactly where I've been sniffing around...
Fuel pump was super cheap at $40, so instead of wasting time testing pressures, I replaced it. Intermittent issue persists.
Carburetor was yanked, disassembled, and thoroughly cleaned before reassembly and re-installation. I didn't find anything obviously unusual whilst in there... jets were all clean without obstruction. Intermittent issue persists.
Ignition coil including the lead wire , also really cheap at $60, so I'm just gonna replace it too. Then I can be certain that any gremlins go out the door with the old part.
Spark plug, $5. Turns out the existing plug is actually not the recommended plug as its heat rating is too high. Though I doubt that would cause the issue, its being replaced with a new one at the correct heat rating.
I was hesitant to start getting into the engine, but if the ignition coil and new plug do not resolve the issue, then valve inspection and confirmation of their clearances is were where I was heading.
Overall, the issue presents like an intermittent fuel or spark problem. Quickly tapping the accelerator to rev the engine repeatedly sometimes results in a major bog, almost to the point of stalling out if you do not let off. But only sometimes... If the valves were out, or there was a compression issue, it seems to me the problem would be far more consistent. I am leaning towards a weak spark compliments of either a faulty plug or ignition coil, so I will post results here when the new parts are installed... hopefully by the end of the week.
Thanks for your actionable input; much appreciated!