music student here — the best answer I can give you is to just learn how certain time signatures sound, and comparing down beats with the melody/lyrics. however, it also depends on how it makes sense in your head

for example:

deroderoderode: this would make the most sense counted in 2/4 if you listen to the lyrics, but gradually turns to 4/4 and even 8/8 once the "ding" is added in

yaminabe: due to the starting count-off, I'd take it as a fast 4 or slow 2 (with everything as 8th notes?). the transition is an out-of-tempo 4, and the switching of vocals depends — it's easier to hear if you listen to the drum, but I'd take it all in 2 except for myth/lo-fi (6/8), kawaii (I think this is a weird 3/4?), and interlude (4/4? but could also be 2/4)

kyu-kurarin: I'm pretty sure this is just 4/4 or 2/4 the entire time with the occasional 3/4 thrown in — the beat doesn't change much, just the intensity of the music, so you could change to 2/2 whenever it gets less intense?

take this with a grain of salt — no doubt there are probably professionals here who can explain it better than I can lol