I'm just playing on my world for 1 day and I noticed that every 2 chunks rendered and more mobs to spawn more delays and lags tend to happen, World details: Fire spread off, Peaceful difficulty, Do weather/day cycle on
My settings: Render distance=5
Vsync off
Texel anti aliasing off
Fancy graphics off
Clouds off.
(My texture pack enabled doesn't decrease Frames per second instead it increases it
So in vanilla my fps would be lower and more delays)