I've tested a few guest post providers recently, but most links did not move rankings much.
this is an ambiguous (and probably incomplete too) statement, because...
1) tested them how??
You've built them and then removed them few days later when you've seen that they don't improve the rankings? Did you even index them? Were they topically relevant and / or d0follow? Lots of questions on this point alone...
2) "a few" guest posts rarely help in SEO, especially if...
- the guest posts are not relevant
- the guest posts need time to mature (if you know how guest posts work you'll know that they are placed on pages with 0 authority initially, so their value grows with time, and with the owner of the website where your guest post exists actively promoting that page and / or building its authority)
- the page on your site (that the guest posts links back to) targets highly competitive keywords (not all keywords are suitable for guest posting, some of them - the casino / gambling ones for example - benefit from PBN links more than from guest posts, so building guest posts for such keywords rarely yields good results, so I'm not surprised that your rankings didn't move if you operate in such niches)
3) are you certain that it was the guest posts' fault that your rankings didn't move much?
Because, like I said, it could also be a niche / keyword problem... or a site structuring and optimization problem... or a topicality problem... or god-knows what else...
Are niche edits and outreach links working better now?
as long as backlinks are a ranking factor (and they still are) all types of (quality) links will continue to work, no matter if it's niche edits, PBNs, guest posts, or press release links... heck, even profile links can work in certain aspects (they help boost trust and a bit of authority).
And "outreach links" is a general term that includes all types of links (even press releases are outreach links if you actively outreach to journalists / media outlets to close backlink deals with them, so...)
Would like to know what type of link building is giving the best results currently.
it's not a one size fit all situation, it really depends on...
- what niche you're in, and which keywords you target
- how much google trusts your site
- what the competitiveness of your keywords is like
- etc