I recently bought a super lightweight butyl (normal) inner tube to replace the one I carry around as a spare/backup. On my most recent bikepacking trip around the Bear Bones Bash route I'd stuffed a tube into my rear frame bag, to the point that it was nearly bursting at the seams and very difficult to actually get anything in or out of the bag.
I did a little research and found the Tubolito S-Tubo (the lightest Tubolito tube), and some other tubes from other brands that are basically the same. The reviews for these tubes were mixed though, more mixed than they should be. The consensus seemed to be that if they worked, they were great, but sometimes you'd go to use it and it wouldn't hold air, or puncture randomly at the valve. Not something I wanted to happen when I'm having to resort to putting a tube in, probably miles from anywhere and probably getting rained on.
So while the weight and space savings were huge – the S-Tubo is 200g lighter and significantly smaller than the butyl tube I've been carrying, the risk of it not actually working when I need it to outweighed the benefits, and even if it did work I didn't want to constantly have the thought that it might not work in the back of my mind.
Instead I ended up buying a lightweight butyl tube from Maxxis. They do several ranges, which are confusingly named, but the lightest of which is 'flyweight' (maybe it'd make more sense if I was into boxing?). It's advertised at 95g for the size I bought and I weighed it at about 110g (why are manufacturer weights never realistic?).
The tube I'd been carrying was a fairly average tube from Continental and weighs 245g, so while the Maxxis tube doesn't save as much weight as the Tubolito tube, I feel much more confident it will actually work when I need it to (and be patchable with normal patches).
You're probably giving up some puncture resistance by using such a lighter & thinner tube, but I'll see how it goes. The hope is that I never use it anyway and that if I do I can still patch it if I get a puncture and swap back to tubeless asap anyway.
The Maxxis tube is also a lot cheaper than the Tubolito tube, and still a lot smaller than the old tube. So for about £8 I've saved about 130g and fair amount of space, which isn't bad for something I don't want to be carrying in the first place.