Hi Flalar,
Just to let you know that this is not an authoritative F5 answer, ok? I'm an F5 employee but this is just my opinion based on my experience of years working for F5's Engineering Services and interacting with HTTP/2 Product Development team. I would (myself) recommend increasing concurrent streams per connection to 100+. I don't think it can cause any negative impact on performance at all. In fact, it's the opposite! It should be much better since your TCP/HTTPS/HTTP/2 connection can potentially be reused for multiple streams rather than having to establish multiple connections as is the case with old HTTP/1.1 protocol. A regular browser typically opens multiple HTTP/1.1 connections to a website to improve user experience by loading things simultaneously/in parallel. HTTP/2 ready browsers can do the same in 1 TCP/HTTPS/HTTP/2 connection instead by using multiple streams. I personally don't think you will hit any limits in the appliance by increasing concurrent streams.
All the best,
Rodrigo