What is the best torrent client to use on a router (asuswrt-merlin) and how to configure it for optimal resource usage?

Question

ASUS

Based on the Asus RT-AC68U router, I am making a kind of mini-server for torrents, file storage and other things, a hard drive formatted in ext4 is connected to it via USB 3.0. The question is in choosing a torrent client that is undemanding to resources and allows you to interact with it from under windows.
Picked up:
1) Transmission (it noticeably slows down the system itself. When the hard drive was formatted in NTFS, it hung itself tightly and did not respond)
2) Deluge
3) Rtorrent + rutorrent (there is only a web interface, set up automatic transfer of torrent files using the extension for the browser, it also does not work fast enough and eats up both processor cores)
Tell me, which client, according to your experience, is currently the most optimal for the described use case, and what advice on setting them up (best practices) (number of connections, RAM limits, etc.) can you give?

Answer 1

For this purpose, I liked Aria2 most of all.
This is a purely console utility, it is controlled from windows via a web interface (meaning that the web rises to windows and interacts with the loader using JSON-RPC via
WebSocket)
I have it on a router with 16 mb RAM.