for some reason, the app is letting me put in 25 credits and supplement $400 add on to get on the Eupgrade waitlist

Have you actually done it? The $400 is $200 per pax as the non-SE add-on for PY to J upgrades on international routes.

It's 17 + $200 per pax.

What’s a decent bid upgrade offer for an overnight Montreal to Lyon from economy to J
in about 7 days time. Still showing J8
$100 an hour for the flight ?? Haven’t done bid upgrades before for over nights

Like it says in the Wiki - no one knows. Bid what it is worth to you.

The $100/h value figure has been tossed around before, but it's a personal preference.

Bid accepted on AC 1280 right at T-48 with J9 showing on expert flyer. The flight went out with about 8 empty J seats as well.
Bid was just over the minimum amount.

Curious how much was the bid amount for that route?

It started at $300 or $305 and went up to $800 or so.
My accepted bid was $315.

Ended up bidding the minimum and getting it for LAS-YYZ at T-48. It went from J9 to J5. Now I'm wondering if I could have maybe not bid and gotten a bump to at least PE as a M fare at the gate with it the flight currently being J5 O3 Y8 M8 at T- 31

I think I may have been quick on the trigger given my experience in Y on the way here and being so far down on the upgrade list

AC usually does not give out complimentary upgrades. If you do the gate upgrade, it is usually the LMU amount or published eups.

But in your case you may indeed get a great LMU price when checking in.

I wasn't referring to a complimentary upgrade. I had meant rather than bidding for an upgrade, I maybe could have let the flight upgrade list go to the gate and see if I would have been able to score an eUp at the gate through regular means considering where the fare buckets are now with me as an 75K, CC, M fare

Got. I flew this route last year and just went up to the gate and asked for an update to J. Paid 6 eups and got it.

Do you know if you can you do this at the MLL desk or does it have to be at the gate?

Never done it in MLL. But both gate agents and customer service agents can do it, so I expect an MLL agent should have no problem.

Looking to bid upgrade YYZ-YVR on Feb 25. Minimum amount is $370. Can anyone advise what would be the best scenario here?

The best scenario is that you get the upgrade.

That obvious answer aside, there's a Wiki entry that speaks to this scenario.