CP differences in PVP & do IV's matter?

Movesets seem to be what matters more over all, but I think in this comparison, its CP

By capping CP, the IVs of the pokemon become fairly irrelevant, except for the balance of total stats (base + IV). A pokemon with perfect stats at a given level, and the same species of pokemon with the worst possible stats, powered up so the CP is comparable, perform about the same in PvP.

What matters with IVs is the balance of stats. Consider Gengar, very high attack, low stamina and defense. A Gengar with 0 attack, 15 stamina and 15 defense, at a given CP, will likely be more useful in PvP than a perfect, or one with a 15 attack and 0 stamina and defense.

There should be some ideal stat balance, and when the pokemon's IVs bring it closer to that ideal, it's stronger at a given CP.

You're correct to save more stuff now - we still don't know exactly what's best for PvP, although high IVs are still important for Raids and Gyms (PvE) as well as for the Master league, where there is no CP cap.

I see my pvp mons in a "price is right" style. Insted of looking for 90%+ ivs i look for the closest to the cp caps (xx95) with marginal stardust investment. My feeling is the closer i get to the cap the less and less individual stat IVs will affect performance.

The next step is finding a good synergy of moves and resistances

Best IV spread for most pokemon in PvP are generally speaking 0-1-2-3/15/15 to maximize defensive stats below a certain cp cap.

IV don't make a big difference in CP capped PvP, but the best IV spreads for all pokemon in those leagues generally involve low attack IV. Out of the two, do the one that hits closer to 1500.