The issue with comparing N165 and Re23 isn't so much RQ (relative quickness), much more one of specific energy. N165 is a relatively low energy propellant and I'm assuming given the MVs being quoted for various cartridges Re23 is one of the highest energy products on offer.
The result is that there is often insufficient capacity in the case to get enough N165 in to achieve the desired velocities, and I suspect sometimes to produce pressure levels that produce the most consistent and efficient burn.
The upside of N165's relatively low energy is that it is widely regarded as 'cool burning'. If you can get enough into the case to achieve the velocities you want, it'll likely give the best barrel life on offer, only Hodgdon H1000 having a similar reputation.
Doing a bit of modelling in QuickLOAD (using 243 Win with the capacity marginally reduced to reflect 6mm Creedmoor), 2.88" COAL (for AI type magazines) and the 107gn SMK, N165 will just achieve the >3,000 fps node at the cost of a bit of charge compression. (3,025 fps in a 28-inch barrel with a 99.9% charge burn and ~60K psi PMax.)
Run it again with Re22, and you gain another 104 fps MV for the same charge weight giving near identical pressure, charge burn % and still with a compressed charge, but now barely so at ~101% calculated fill-ratio. Re22? The nearest thing to Re23 in my old version of QuickLOAD.
Then onto Alliant's data on its web pages to compare Re22 and 23. Rather to my surprise, there aren't any data for either powder in the 6mm Creedmoor, but there are for both powders in the not too ballistically dissimilar 243 Winchester. With a rare bit of luck for such Internet and paper exercises there are two 100% comparable loads, both sets containing data for the 100gn Speer BTSP COAL 2.625" in Winchester brass and ignited by the F210 primer in a 24-inch barrel.
Re22 .............. Max 45.5gn 2,966 fps
Re23 .............. Max 45.1gn 3,140 fps
So (by a rather tenuous chain!

) it appears we can expect roughly 100 fps higher MVs with Re22 over N165 in this cartridge, and another 100 fps again - maybe more - with Re23.
N165 is single-based, but all Alliant grades are double-based. AFAIK, the company doesn't quote nitroglycerin percentages for any individual Re grade, but if Re22 and Norma MRP from the same source (Bofors in Karlskoga, Sweden) aren't the same thing under different labels then they are damn close. Norma quotes 11.5% nitroglycerin in MRP. So pushing yet another tenuous connection, (2020 gets off with a high degree of tenuity here - yes, that's real word!

), I'm assuming Re22 must have similarly high levels.
That raises another issue - just how is Bofors / Alliant Re23 achieving such an MV increase over its sibling very high-energy, very high-performance Re22 propellant? I'd love to know how Re23 manages to produce another whole step velocity change over very high MRP/Re22 performance levels. Given how close the charge weights are from Alliant in the 243 data, I would hazard that they've been loaded to similar pressure levels and this isn't a case of the lab pushing one right up to maximum SAAMI pressure and not the other.
I then went and had a look at my brand new Sierra handloading manual edition VI as it has loads for new powders (Alliant and IMR Enduron) in a gratifyingly large number of cartridges. Sadly whilst Re16 figures (I'll go further and say 'stars') in a number of this size / expansion ratio class of cartridge including 6mm Creedmoor, Re23 doesn't show here with the (strange

) exception of the 6mm Rem. It does appear in the larger case cartridges such as the 7mm and 300 short magnums. The slowest burners given for the 6mm Creedmoor tables are H4831sc and Superformance in the 107 and 110gn MK tables. Sadly although the new edition Sierra manual tables haven't become the 100% Viht free zones of competitors such as Hornady, Viht loads are thin on the ground N140 (lighter bullets only) and N540 (heavier weight bullets only) in the 6mm Creedmoor tables.