I ran a stress test on one of my apps. I had 5 columns and 120,000 rows to start out with. This was loaded into a single list. While it did load everything…I think…it really pushed my computer and phone to their limits. Refreshing the sheet in the builder took a few minutes to load the entire sheet and the builder was sluggish, although that could have been the entire browser being slow. I’m sure the browser is caching all of this between the sheet, the builder and running a published version of the app all at once.
Backing down to 100,000 rows, things were slow, but slightly more responsive. The app on my phone stopped crashing.
At 75,000 rows, I’d say things were bearable.
At 50,000 rows, I’d say most operations are normal if not just a hair slower than usual.
Obviously most people would have much smaller lists and sets of data visible at one time. I would advise against loading 120,000 items in a single list. 
- Disclaimer: My computer is a few years old, but decent, although I have about 100 browser tabs open.
My phone is an old cheap model and will lock up if you look at it wrong. I have around 50 browser tabs open on that.
Results would probably vary depending on the equipment you are working with, so if you have something faster, it may work better.