For a given cam, all else being equal, can you useless spring rate if you have titanium valves and retainers? Seems like you'd need less spring to control the valve which should help power and longevity.
Yes, but you have to have access to some really fancy equipment and information to know exactly where you may be getting into valve float and how much less pressure & rate you'll need with lighter valve train parts, or how much higher you can rev the engine with the same springs. Then there is the question if the lighter weight is worth the trouble for durability or if the engine actually benefits from more rpm.
You can have valve float without ever realizing it, until something breaks. If the engine is nosing over from valve float, it already started way before that.
You can also consider beehive or ovate springs, which have much smaller and lighter steel retainers. There are steel retainers that have been lightened as well.
