The difference with most eco liquids is the reduction in phosphates, which is fine if you're in a soft water area, but utterly hopeless for washing if you live in a hard water area. I can explain the chemistry if you want, but I'm just back from a run and my brain is too hot to do it just now, so you might as well google it.
Smol's only claim to eco-ness is the packaging being made of cardboard. It also uses phosphates. I tried them, they were fine, but so is Fairy.
I use Bio-D liquid, because I need some sort of smell in there and the Juniper is natural and doesn't bring me out in a rash. I can't remember why we stopped using Ecover. There was a reason. I live in a soft water area and buy in bulk from
https://biggreensmile.com. They have a British warehouse, if that's a concern. The only other effective eco stuff I've come across is.... Oh what was it called? Had a clownfish on the bottle. Attitude? Looks like it has a penguin now. Don't like Method, it's itchy. There was another one, but I can't remember the name and I've only ever seen it in Realfoods in Edinburgh anyway. They don't have it now, so I assume it's not longer made.
Mind you, I haven't tried all of the vast range that BGS have on offer.
We use Dettol laundry additive. If Mr Bait has been particularly sweaty out on his 10-15k, I use Halo
and Dettol. (The sensitive variety, which has no added perfume.)
Sam