I just gave it a shot building JDK 19.0.2+7 natively on the V2. One with my original zero build which took 3:56hrs and once using the server variant which took just 1:26hrs. I call that a massive improvement!
Will have a go at trying a few projects with it to see what real life performance and stability is.
I’ve been using optimised buids for jenkins RISC-V agents (various different versions but including 19) so it seems to work OK 
So far haven’t encountered any problems with JDK 19 an the server variant. And no, I would not call this an “optimized” build. It just has JIT and doesn’t run in interpreted mode. Whether that JIT is currently optimized well, is quite the different question. Fater than interpreted but probably not as fast as it could be?
Arch POWER ships OpenJDK 19 w/ server variant enabled by default since for about 2 weeks or so now.