Honda 5AT and TES-295

I assume:

Thicker fluid = higher line pressure = harder shifts? I could be wrong.
Your assumption would be correct. Where I live it gets cold and I have corrected hard cold shifts, and harsh flare ups on more than a few BYBA transmissions with a 3x3 drain and fill. I have a 2002 W/255K, with a J32A2 Type S and I'm not always nice to it in 3rd, the gear that tends to grenade the trannies. That said, I would not condone using a TES-295 fluid. I use it in my Allison though.
The Accords and TL's switched for the 07 model year I think it was. Not sure about the Oddy's, and I think the Ridgeline was always a 4 shaft unit, but I could be way way off on that. I don't know as much about the Ody/RL's.
Accords, 06
Odyssey, 05
TL, 07

The rest, IDK, but the Odyssey was first, then the Accord, the Acura line was last, or at least the TL was last.
The 05, Oddy, and 06, 07 Accord transmissions will go into the 1999/2005 TL's. The gear ratio's are not exactly the same, but close.
Got a FWD Honda with a 3.5L V6 and 5AT (PN4A). It is higher miles, 185k, but shifts good. I want to keep it shifting good for as long as that J35 engine lives, all while being able to tow at 50%-100% of it's rated towing capacity pretty often. With that in mind - are there any known definite downsides to using a TES-295 ATF? I'm thinking Mobil Delvac ATF. I believe Honda recommends DW-1, but that fluid is more about MPG, rather than maximum protection. So I do expect a small MPG penalty, but just wondering if there is anything else that could cause issues in the long run.
With reasonable maintenance your J motor will outlast pretty much everything else on your vehicle. I would suggest Honda's fluid for the trans, and drain and fill maybe every 10/15K. It's only going to drop 3 quarts or so.
They added some oil jets to the 3 shaft units, and backfitted them to the earlier units under recall as well, pretty sure though that the new trans didn't arrive until 2007. Can't confirm that though. 2007 was the first year of the Ridgeline though and I'm pretty sure that they just took that trans and spread it across the line at that point, more or less.
Someone posted a chart or something with details about the various transmissions Honda built, timelines of their release and which models they went into, and so on. Can't remember which thread it was (here) but it was recently too.