Ewaka is the go to provider, however they are based in the netherlands so your speed may vary. An alternative would be frugal usenet as they also do have a US based server, but Ewakas retention is way better. If you use SABnzbd as downloader you could even add both frugal and ewaka with the same priority if you can't max out your speed with one. Maybe you can try ewaka for 1 month first and see if it's good enough for you.
I saw that you mentioned giganews, however based on a quick search I saw that they seem to have a really bad reputation nowadays
Usenet Indexers:
I can't tell you anything about nzbplanet as I never used it, but nzbGeek is a good start. You'll need a paid membership for every indexer though, a free membership won't allow for *arr automatisation.
https://drunkenslug.com is great indexer, however registrations are closed at the moment - you can easily find an invite though if you lurk around here.
Usenet providers:
Ewaka is the go to provider, however they are based in the netherlands so your speed may vary. An alternative would be frugal usenet as they also do have a US based server, but Ewakas retention is way better. If you use SABnzbd as downloader you could even add both frugal and ewaka with the same priority if you can't max out your speed with one. Maybe you can try ewaka for 1 month first and see if it's good enough for you.
Special links that lead to the cheapest offers:
I saw that you mentioned giganews, however based on a quick search I saw that they seem to have a really bad reputation nowadays
Usenet Indexers:
I can't tell you anything about nzbplanet as I never used it, but nzbGeek is a good start. You'll need a paid membership for every indexer though, a free membership won't allow for *arr automatisation.
https://ninjacentral.co.za/ just opened registrations yesterday, they are also quite good.
https://drunkenslug.com is great indexer, however registrations are closed at the moment - you can easily find an invite though if you lurk around here.