So im upgrading my system again, I first had 1 Q 15 sealed with the High qts option, then I wanted to go ported, so I bought another Q 15 with high QTS to be the exact same as the first sub. Im now going to rebuild my wall and run 4 FI Q 15s (later ill probably SP4s) the next 2 subs I get will have all the same options as the other 2 but should they still have High QTS since im running ported? I know high QTS is not optimum for vented enclosures, but should they all be the same when it comes to QTS?

Yes, you would want them all to be the same driver. Meaning the same Qts.

No, ideally you would not want to run the high Qts drivers ported.

If you are looking at purchasing 2 new drivers, your best bet is to sell your current subs and just purchase 4 new "low" Qts drivers.

But why is low QTS better for ported?

What would be better, 4 Qs with high QTS ported? or 4 SSDs with low QTS

High QTS removes metal from the subwoofer reducing the amount of BL. Drivers with low QTS are typically always more suited for ported enclosures.

A unitless measurement, characterizing the combined electric and mechanical damping of the driver. In electronics, Q is the inverse of the damping ratio. The value of Qts is proportional to the energy stored, divided by the energy dissipated, and is defined at resonance (Fs). Most drivers have Qts values between 0.2 and 0.5, but there are valid (if unusual) reasons to have a value outside this range