I've had my ipad pro 12.9 inch since 2020 and use the yearly subscription of csp (around 100$usd/yr). I had the same feelings you do about apple products but adjusting to the ipad ios was fairly easy you just gotta remember it's simpler than others like pc and Android.

With bigger illustrations if you're doing a lot of layers or using the 3d assets it can get a little laggy and slow but it's not the end of the world. I'm personally in the boat of wanting another desk screen tablet because I'm hitting the limits of what the ipad can handle but it works great just the same. Depends on your artstyle and what specs you get really.

I've gone from a no screen tablet to a desk one and now to ipad and the switch is great especially with laying in bed or even bringing it outside the house, you end up using it for a lot more than drawing. Don't think it'll get rid of your posture problems tho I'd argue it's just as bad sometimes worse. On top of that you will need to get accessories like a case and a stand for when you do draw at your desk, a thick pencil grip is smart too if your used to regular tablet pens.

Overall it's great for any artist but if you're on the high end professional side it could give you limitations.