Hellobee Boards

We have the first one. It's been wonderful!

We used the second with DD and she liked it a lot. She was an odd child who didn't like the stand alone potty but loved the big one. We put a command hook on the wall next to the toilet to hang it when not in use.

I don't have any of the suggested, but we use a seat similar to the bjorn with a step stool. It hangs on our towel shelf and DS can easily put it on himself.
The first one would be awesome though!

We have the first one (or something very close) on the 2 toilets that LO uses. It's great! It's a soft close too which is nice. She actually trained on a little stand alone potty because she randomly trained so young, but we phased those out once she could climb on with a stool and we love them! She doesn't fall in and we don't have a separate device to deal with.

@Mrs. Lemon-Lime: We have the Bemis lid on our bathroom toilet but for boys, there's no splash guard in the front so my son was peeing out the front a lot. Also, when they start training, they like to just sit there forever and the seat was making his tush uncomfortable. So while I think the seat will be useful ultimately, for now we have one of those cheap padded/cushy rings that go on the toilet seat (we have two - one is the Mommy's Helper one and one is the same thing from Walmart - they were like $8). He finds it much more comfy and there is a slight splash guard in the front that can catch most of the pee if he remembers to keep his penis pointed down. We have a hook attached to the side of the toilet bowl and its part of his routine - he pushes his stool up to the toilet, places his ring on the seat, pees/poops, rips a piece of toilet paper and throws it in the bowl like an offering, flushes, and then puts everything back (hook, stool, etc) before washing his hands.

For the stool, we have 2 of those Ikea $5 step stools and we keep one by the potty and one by the vanity so he can get up and down more independently. We have the Prince Lionheart faucet extender as well.

We have the $5 potty from Ikea as well and for some reason my kid is NOT about the potty - he wants the big toilet - so I'm glad I didn't waste any money on a fancier seat. However, for those who did like potty chairs, my friends have all liked the Baby Bjorn one with the higher back.

We got an integrated trainer like your first link (this one: https://smile.amazon.com/gp/product/B01B3FEQPU), but it hasn't been sufficient for initial training because there's no pee guard and the opening is still too big for my skinny-bummed LO. I think it'll be great for when he's 3 or 4, but, for now we're using an IKEA ring very similar to the Bjorn one you linked.

We loved the convenience of the integrated seat and actually purchased the one you have linked.

While I recommend the integrated seat, we found that the child's seat on this particular model (because it comes off so easily) moved around a lot while our LO was on the toilet, which resulted in a lot of damage to the adult seat. We just put our original toilet seat back on because I was tired of looking at all the markings and our LO doesn't like the child's seat anymore!

TopSeat, Delta & Kohler make a similar seat which appear to have a more secure child's seat

We have both types - the first was great for my daughter, but awful for my son because there isn't a pee guard. I think it set us back in potty training because he didn't like the pee squirting out - it's easier for me to hold him on that toilet than have him sit on the integrated insert.