In every world I've played in on any 1.17 prereleases and snapshots, there is constant lag that affects both TPS and FPS, making the game extremely off-putting to play. Upon leaving and rejoining a world, however, the lag and stuttering is even worse, and is much, much more visible in both FPS and TPS - causing the game to become extremely frustrating to play.

However, this isn't just caused by crossing chunk borders or generating chunks, or anything of those sorts. I've even been getting lag spikes while standing completely still! 

Another extremely weird thing about this is that the game thinks that it's hitting a solid 90FPS, however, it's obvious that it looks much closer to about 25-15FPS with all the stuttering at its worst.

The fact that I have a good CPU and GPU makes me believe that 1.17 will be even worse for players on any devices that aren't top-of-the-line, and likely even straight-up unplayable for them.