The only way to know is to do a split batch yourself.
On attenuation and mash temp, I'm listening to an episode of Basic Brewing Radio right now where Sean Terrill (sp?) is on discussing his data on mash temp vs attenuation for three strains (one lager, one Belgian, and the Anchor Liberty strain). The Belgian (d'Achouffe?) strain behaved as brewing dogma suggests it would, lower attenuation at higher mash temp. The lager strain didn't have enough data points, but is kind of flat in the middle of mash temp range, and lower attenuation on either extreme end. The American strain threw dogma out the window and had the same degree of attenuation regardless of mash temp. I could be slightly misremembering things, but you can find the data on his blog. So moral is don't assume adjusting mash temperature will change attenuation. It might not.
On to the other part of your question... I just bottled a split batch 95%MO/5% light crystal (~C40) fermented with S-04 vs 007. You'd think 007 would finish lower, but they both finished at the same FG. Tasting the hydrometer samples, I swear that S-04 had more mouth feel than 007. Could be glycerol. Could be a small amount of diacetyl adding to the feel. Could be different sugars left in the beers even though FG is the same. Who knows? But there's more to mouthfeel than just unfermented sugars. In fact, those Brulosophy experiments where they test two mash temperatures and get beers well over 1% abv different, yet are seemingly identical to tasters would support this.
Sorry. I know you wanted and answer other than "brew a split batch".