As to potty chairs, the ones made for kids are really to small and are essentially useless for adults.
For those physically capable of squatting antique china or enamel chamber pots are commonly available, but require a lot of muscle tone. On the other hand, the usual squatting position really helps one poo. Also, if you have to use a chamber pot, any audience can see absolutely every detail. Modesty is impossible.
Real, adult potty chairs, called bedside commodes, can be very useful, especially if you like powerful laxatives, suppositories, or enemas. One can place the commode at bedside, with the pail in place, ready for instant use and have no worries about messing the carpet on the way to the toilet.
A couple of user hints:
It is a good idea to place a disposable Cuux pad under the potty chair, in case of leakage, accidents, or splashes.
Also, put a couple of inches of warm water with a few drops of dish soap in the pail when you set it up.
The water will cover the poo and it'll stink a lot less and the dish soap will make the pail easier to clean when all done.
There are also products like Unicorn Gold Spray to hide smells.
There are a variety of bedside commodes available, staring at about $30 new. Many fold for storage, but the cheap ones tend to be uncomfortable.
This is a commode that I've found to be comfortable, sturdy, and well made:
https://www.platinumhealthllc.com/products/ultracommode-voted-1-most-comfortable-bedside-commode-chair-soft-warm-padded-and-foldable-xl-seat-with-100-open-front-padded-pivoting-armrests-adjustable-height-free-commode-pail-blue
The arms fold down, so transfer from bed-lying to poo position is easy. Also, the pail can be removed from the front allowing full access to all playground areas while seated.
As to being watched on the potty, it can be really embarrassing. When in hospital some time ago, I got very constipated from the meds. I refused laxatives because I was confined to bed and didn't want to be made to poo uncontrollably on a bedpan. So the doctor ordered a large volume enema.
Two nurses came in, set up a commode bedside, prepared a large, full, clear disposable bag of soapy water and hung it on the IV pole. I was a bit weak post-op, but they filled me with the whole bag and then positioned me on the commode and steadied me there while the enema worked. When I'd finished pooing, one nurse steadied me, while the other wiped me clean, and I was put back to bed. Embarrassing does not begin to describe the experience, but the enema was successful. All in a day's work for them, I guess.