For me, option 1. Let's not go so far as 'it changed my life' but I don't use legacy keyboards at all. For all typing of all forms on my Surface Pro PC I use the textblade. I use voice translation for most of my text messaging on my Pixel 2, but if the messages are important or long, I jump the Textblade to the Pixel, type and edit the message, and jump back to the Surface.
I don't travel, so the size and convenenience aren't life-changing. If I did, I think it would be one of things, like wheeled suitcases, that you take for granted as a enormous convenience. Imagine if only Samsonite had wheels. Every other suitcase would be an incredible (and literal) pain in the neck. That's the kind of advantage the Textblade has.
OTOH, the small size is nice. When I eat while I work (all too often) I can push the little thing up toward the Surface Pro and not have to jostle with a huge keyboard and its 104 keys.
Typing and editing with hardly any use of a mouse is a big deal and I think that's understated. All the keyboard mapping, edit keys, movement keys.
I suspect the app is also a big advantage, but since I make hardly any use of my old iPad (having an iOS device is a requirement to be a tregger), making quick changes to the keyboard maps and features and macros and so forth is too cumbersome, so I don't. But ask me again when WT introduces their TextBlade App on some platform I own, whatever they choose, that doesn't require iOS. That will be huge for me and I'm dead certain that will open a lot of pathways to make the TextBlade easier. I'll fire up the app, add a convenience feature, and it'll be there almost instantly.
Device screens are my interface to content received from the world. They are rightfully the most important UI aspect of handheld and workstation devices. But keyboards are my interface to content I deliver to the world, as a manager, as a software developer, and as a friend and family member. When it's easy and powerful and works just the way I want it, well, maybe that is life-changing.
A mechanical keyboard just doesn't have a chance against a software-driven, connected and intelligent Textblade that's a perfect fit both physically and mentally. How could it? Those old keyboards are like a suitcase without wheels.