5 or so days in late June. Not sure if I should use my own gear or get the Duluth pack from an outfitter. Thoughts?

Does it affect single-trip vs double-trip portaging at all?

Depends. Lots of unknowns - are you going solo, tandem, group? If all your gear fits, use it, just make sure to waterproof everything in dry bags or other somehow. The outfitter will usually provide a heavy plastic bag liner (make sure to ask...) with a portage pack to help with waterproofing. Portage packs are also one large pocket, where a backpack has multiple, so it's usually easier to fill the portage pack. Backpacks are also narrow and tall, which can make it a bit harder to fill with bulky gear, but still will work fine. Also note that backpacks sit higher and may interfere with the yoke trying to portage a canoe while wearing it. If you intend to single portage, this may be an issue. Best if you can try this out first before heading to canoe country. Portage packs are designed to sit lower and provide the needed clearance with the portage yoke. Also of note, the backpack may hold more water due to more fabric and cushioning when wet - rain soaked or bilge water - making it a bit heavier and take longer to dry out. Good luck on your decision.

As portagedog09 wrote, the Osprey 70L pack will be a problem if you intend to wear it and portage the canoe at the same time. It is a tall pack and will interfere with the portage yoke.

If you go with the Osprey, I'd remove the hip belt.
They have a habit of getting hung up on the gunnels when loading and unloading.
Downside is now all the weight is on the shoulder straps which aren't designed to carry all the load so would keep the overall weight down. Might work well for bulker lighter items.

Duluth pack gets my vote.

I'd say, use what you have. At least initially, then you have more info on your own useage.
I used a GG Nimbus Trace Access 60L as well as a Camp Trails Torrid 2 in a Wenonah Advantage solo. Never an issue with the hipbelt, nor anything else. But I did double portaging all the time. The Osprey rides higher than my GG Access and would probably interfere more with a carry thwart.
I tried more traditional portage packs, decided they were not for me and I could get by with just about any pack that fit between the gunnels. I have used external/internal frame backpacks in tandems and solos without problems.
While some internal frame packs may weigh more (my GG 60L weighs just under 4 pounds empty), they usually make up for that in comfort. Volume for volume they soak up no more water than a portage pack and fit into my canoes just as well. While my internal framed packs have a few external pockets (just like many portage packs) it has just a single compartment. A single waterproof bag to fit the volume keeps all my gear dry.

butthead

Went with rental Duluth packs on our first trip. A little more bulky and awkward, but the size and simplicity takes some of the hassle away from needing to be' efficient with your gear and packing. The handles also made it nice for 2 guys to remove and place into a canoe together on long days with many portages. We also saw rain on the last days of that trip so it was great to dump the soaked Duluth packs at the outfitter when done and not be hauling them home with us.

That said, we now use internal frame packs and have had no issues. Packs lay flat perpendicular to the canoe and don't ride any higher than a Duluth pack. A little more strategy and efficiency is needed to pack, but otherwise no differences. We don't single portage so that has also not been an issue.

Ask your outfitter if they rent any other packs other than a Duluth Pack. I have several Duluth Packs, don't get wrong they are great packs, very durable, nostalgic, and fit well into canoes. However I have several of the CCS hybrid packs - CCS Explorer, CCS Pioneer, CCS Food Pack, CCS Quad Barrel Pack, and a CCS Bushcrafter. With the padded shoulder straps and hip belts they are way more comfortable than the standard Duluth Packs. Many Outfitters have CCS, Granite Gear or others.

Northwoodsman: "Ask your outfitter if they rent any other packs other than a Duluth Pack..."

I thought this was going to bring up the Iva Trump visit to Duluth Pack last year. Use 'em if ya got 'em, but don't buy more.

Thanks for the reminder! I just ordered a Duluth Pack as a Christmas gift and now I can feel even better about it!

Merry Christmas! Too bad inflation is so horrible right now and everything is costing more, and we’ve got massive shortages! Most expensive Thanksgiving dinner ever and Christmas is going to be even worse. Covid hasn’t seemed to go away either!

Ryan

Duluth packs were my go to pack for many years of canoe trips. In my later years though I have gone to the internal frame packs. I simply can't carry as much as I used to. The hip and chest straps are a big help on rough portages, the Duluth packs lack these and unless the shoulder straps are real snug the pack sways a little at least for me. I don't like loose things and I make good use of the pockets to hold bug spray, sun glasses, water filter etc Duluth packs don't have pockets.
I still have one Duluth Pack left (the other ones have been "borrowed" and gone for ever) and still use it often just not on trips with portages. My 2 cents.

I don't think one is expected to carry a duluth pack without a tumpline, it's very uncomfortable. CCS or Granite Gear canoe packs can be carried without it, but at least on GG it's used to be an option.