I don't have direct answer to the question, but I generally don't add public trackers to my (public) torrents. DHT/PEX usually works fine for me for finding seeds on the occasion that I do need something from public torrent sites.
I wonder whether adding additional trackers only increases the speed in which peers are found or whether it also substantially increases the likelihood of finding peers.
Trying to actually restore is the best way to ensure the backup works. But it's annoying so I never do it.
I usually trust restic to do it's job. Validating that files are there and are readable can be done with
restic mount
, and you've mentioned restic check.The best way to ensure your data is safe is to do a second backup with another tool. And keep your keys safe and accessible. A remote backup has no use of the keys burned down.