You really need to acknowledge that the smaller the stroller, the less it will have an upright seat. It is simply too much to ask, design-wise, as the stroller is made to be super simple, light, and cannot have a completely upright seat at that.
The Aer is the best option of yours, size-wise, as it has a tall seat back. However, the backrest positioning desn't lie flat, and is a bit complicated, with side zippers, which, seeing you want a hard backrest, might be a problem for you. Quality-wise though, it is the better option. The Beezy is a nice small stroller, however a little looser, it is not a super rugged sturdy one. An ok option, I guess, if you need something really small and light. There is, however, a fold in the upper third of the seatback.
I personally would not go for the KK Trig, it is not such a small stroller and also is quite rattly for that larger size. Definitely not a travel stroller, size-wise.
I will also recommend the Recaro Lexa with its larger seat (but it is not upright, sorry, none of these are), or the Ergobaby Metro+, which is nicely padded, has a good enough angle, and overall is sturdier than many others.