WRONG. The hub that has the extra drag probably has DAMAGE, and/or has been improperly adjusted. The ONLY thing, other than bearing condition/adjustment/grease, that might cause higher drag would be any rubber seals on the hub.

as to MOMENTUM... the rim and tire/tube weight lends momentum to the wheel when spun in-frame... I always test for bearing tension with the wheel OUT of the frame, and tire/tube removed... i lay the axle on two open fingers after spinning it up... if the axle wants to turn on my open fingers, it gets readjusted or rebuilt as needed.

"slightly tight"... this will cause heat buildup during use... the product of heat is increased friction... the heating can, and DOES, cause melting of the cones' hardened surface! Ever taken a close look at the "worn" cones with pitting going on? yep, MELTED surfaces. Heat and pressure causes GALLING of the surface. Rust can also promote galling... once again, the extra friction from the rust pitted surface causes heat to build up... add pressure, more heat gets produced, expansion of parts involved further increases heating... whalla! time to replace cones and balls....

A properly adjusted set of hubs does in fact effect your "speed", since a dragging hub bearing set WILL slow acceleration, and yes, TOP SPEED. a bit of fresh, light grease, and proper adjustment makes for a happy, FASTER, rider. Rotating mass also plays into enjoyment... Note all those fancy bikes with carbon fiber and aluminum bits all over the place on them... there are good reasons for those pieces!

Grease... too heavy of grease viscosity will cause issues, too... "FLOWBACK" is needed to keep grease on the bearing surfaces... friction sets in... heat builds... guess the rest... i use a bicycle specific grease... it is light enough to allow flowback, without getting too thin during use.

Reduce any ROTATING MASS to improve acceleration... and get those bearings right, if you have the tools and skills needed.