There's an evident issue with latency in the Quantum 26262. I even have a comparison, owning the Quantum 2 interface and with a Startech Thunderbolt 2 to Thunderbolt 3 converter, the latency is still not noticeable as is the case with the 2626 model. One big bummer is also routing of inputs outputs in the Universal Control, which doesn't exist at all. On Quantum 1 and 2, you can route directly to your headphones and by using Universal Control, you can choose which output you want to route for your headphones. Quantum 2626 has 2 headphone outputs, and still you are forced to listen to the main out on both headphones. Quite inconvenient when it comes to this topic.
Latency wise, I record on 96KHz and typically use 256 sample buffer. 128 samples, and I already have artifacts in my DAW (using Cakewalk Sonar - for the last 15 years). I bought the 2626 for the higher I/O count than the Quantum 2, but I'm becoming disappointed as this issue with latency stubbornly persists no matter what I do. Quantum 2 doesn't have this problem no matter how many tracks I put or what plugins I use, however the 2626 is affected somehow. I'd be surprised if the Presonus staff are not looking into this issue and fix it in a firmware release. I understand that the Quantum series do not support hardware level monitoring and routing, therein the speed of the interfaces, but yet again, I'm suffering of monitoring latency that disables me from recording live instruments, despite the ASIO panel in the DAW reports 1-3ms of round trip delay. I tried with caching, changing cables, but at some point the interface starts building up this latency and becomes worse over time.