Here's my take on Future Cell's (the one who battled future Trunks) power:
It seems that the Future Cell who battle Trunks was considerably stronger than the one who battled Kamiccolo in Ginger Town, because:
1 --> The Cell from future Trunks' timeline displayed an aura when reveling up to fight the boy, while 'Ginger Town' Cell didn't:
2 --> The Cell from Trunks' timeline was apparently already searching for the androids, while the one we had more coentact with wished to avoid a combat until strong enough... plus the fact that he stated Trunks couldn't even defeat the androids, much less him, which gives us with a "Ginger Town Cell < androids" and "future Cell [Trunks' TL] >> androids" scenario...
But I still think that the Cell who was killed by Trunks still wasn't quite as strong as the one who easily dominated Kamiccolo and #17, considering Cell stated, in the main timeline, that he absorbed more people than needed:
And earlier he had stated how absorbing Kamiccolo would take him to nearly the completion of his initial evlution:
So I figure out that Cell's initial evolution is the power he had before reverting himself to an egg, and that once losing power upon doing it, he had to absorb people to get him to that level... but since he had overdone it (like he himself stated) in the main timeline, then the version of the one who wrecked Kamiccolo would still be a bit stronger than the one who fought and was killed by Trunks... who would then be the Cell with his "1st evolution completed", without overdoing it. Something like this, numerically:
Kamiccolo : 375,000,000
Imperfect Cell (vs Trunks, 1st evolution completed) : 450,000,000
Imperfect Cell ('wrecking Kamiccolo', has overdone it) : 500,000,000
Although yeah, I think the "I've absorbed more ppl than needed" might be simply referring to Cell becoming stronger than needed to deal with Kamiccolo and absorb #17 by force. Although I like to think it the way I do since it gives a nice placement to the future Cell who battled Trunks, who would then be considerably stronger than the Ginger Town one but still not quite as strong as the one who equaled #16.