By tempo
140 BPM rap beats
140 BPM is trap and drill territory. Almost nobody raps straight at this tempo - the standard is half-time, so you are effectively writing to 70 BPM while the hats rattle at double speed underneath.
That split is the whole skill here: your bars move slowly, the beat moves fast, and holding both counts at once is what makes trap flows sound relaxed instead of rushed.
Here is the practical version. Count the kick, not the hats. At 140 the hi-hats are firing every 0.1 seconds in rolls and they will drag you along if you let them; the kick and snare are the grid you actually rap to, and they land at half that rate. Once you hear the beat as slow with fast decoration on top, 140 stops feeling frantic.
This is also why so much trap sounds sparse. At an effective 70 BPM you have nearly four seconds per bar, which is a lot of room - so the ad-libs, the repeated tags and the long held vowels are not laziness, they are what fills a bar that wide.
Drill sits a little above this, usually 140 to 150 with a sliding 808 and a different kick pattern, but the counting problem is identical. If you can hold half-time here you can hold it there.
Coming from 120 BPM? The jump is smaller than it sounds, because you are probably already counting half-time. What changes is the density of what is happening between your downbeats.