And let's be clear, it wasn't the app that had problems, the Apple Remote Desktop connection to the machine failed when the speeds got above 40MB/s and the network interface stopped working around 80MB/s.
I think Transmission works perfectly fine. I've been using it for 10+ years with no issues at all on Linux.
I forgot to mention this is a Mac mini/Intel (2018).
Transmission is just a small, floating window with your downloads. Click for more. It fits in the macOS vibe. But I'm a person that fully adopted the original macOS "way of working" - kicked the full-screen habit I had in windows and never felt better.
Can I ask, why would you go FROM Transmission to qBittorrent?
In my case: some torrents wouldn't find known-good seeds in Transmission but worked fine in qBittorrent; there's reasonable (but not perfect) support for libtorrent 2.0 in qBittorrent; my download speeds and overall responsiveness is anecdotally better in qBittorrent, and; I make use of some of the nitty gritty settings in qBittorrent.
Former Transmission user here.
I realise you didn't ask, but you might find some improvements in qBittorrent.