Performance is a hard sell when most of the time is going to be spend waiting on the DB for queries, isn't it? (compared to dbx - anything in Java is going to naturally be larger for this).
Or are you thinking of performance in terms of UX when browsing the result-sets?
But, congrats on the project. It looks great. I can't wait to try it.
Yes, the slow queries stay but there are some differences:
Same result set where other clients can crash, this scrolls smoothly so you can naturally load a bigger result set in the app than other clients would allow you to, It paints the UI considerably faster than DBeaver on my benchmarks, thats after the query has run. Memory footprint for the same result is considerably lower.
Basically, your db client can slow you down even after you have waited for queries so this will fix that.