I'll veer a little side tracked and a little contrary here - just my opinions:

If one carries a Nalgene bottle in a mug-kettle (mugle???...nah), where does the lid to the kettle go?

Tall and skinny kettles are an abomination in windy and/or cold conditions. You can use a wind screen, you can insulate, but they suck in these conditions.

Ditto uneven terrain.

I've (reluctantly) used Nalgene bottles so long that I've some "museum pieces" (HDPE) that are so brittle one can poke a finger thru them and crumble them up (polycarbonate ones MUCH better!)

The large mouth versions (virtually all of ours are that type) are a PITA to drink from - witness the wide availability of "splash guards", Said splash guards rob the bottles of their one virtue - ease of stuffing something like snow into them or dumping a baggie of Hydrolite into the bottle.

Theoretically, wide mouth cylindrical water bottles are slightly more resistant to freeze-up than narrow-mouth military canteens. Practically speaking, there is no difference.

The ideal opening size, IME, is the size commonly found on 20 - 24 oz sports drink bottles (which, BTW, make decent water bottles for the frugal-minded). Don't have one in front of me, but call them roughly 40mm diameter.

A 1.5 - 2 quart pot with lid takes up zero room: sew up a little stuff sack that fits inside the pot and put things you normally stow elsewhere in the stuff sack. Put stuff sack in the kettle.

I have a STRONG preference for a US military canteen cup over the Nalgene bottle equivalent (have and use BOTH). Spend some quality time using both for heating, cooking, drinking, filling water bottles, etc and see what you conclude. BUT - I do not like the narrow-mouth canteen for anything but sipping. If someone would modify the military canteen design to incorporate a 35 - 40mm mouth, I would buy two for everyone in the family, plus spares.

I use hydration bladders almost exclusively for the past few years (Camel Bak by preference, plus sometimes a nifty Platypus roll-up bottle for in-camp use - replaces the gallon milk jug I used to carry). I never put anything but potable water in my bladders. I carry at least one water bottle for 2 reasons: mixing electrolyte replacement and because various incidents over the years have molded me into a "belt-and-suspenders" mindset about water. I have learned to really trust my Camel Bak bladders, so maybe there is some hope for me in the future...

So I DO carry a metal cup (and have used it a LOT over the years). Winters and family also drive me to carry a 2 qt kettle + lid 99% of the time, although soloing (rare these days) I may leave the kettle back home in non-winter conditions.

I hate the taste of water roasted over an open fire (bag melted). Give me carefully melted water in a kettle any day... as the hard-soot blackened exterior of my battered 2 qt pot bears silent witness (don't forget the lid!)

Carry a metal spoon. Lexan, nylon, and lesser plastics will melt at the most inopportune time... I've switched to a titanium spoon from SS and while I love it, I wouldn't miss it if I had to go back to a clunker SS spoon.

Also, for longer trips, a sawed-off wooden spoon is a fantastic implement. But a bag of cheap ones, cut down the handles with a hacksaw, sand end hemispherical, and toss at the end of each trip or do the same to any old wooden spoon and work in a few coats of USP mineral oil + beeswax. (They can get moldy if you don't take care of them between trips).

I warned you I would veer a little askew of the main topic... anyway, these are my opinions. <shrug> use what works for you. But DO always carry a metal mug or kettle!

Tom