who's greatest bullet player of all time: andrew tang, alireza firouzja or magnus carlsen?

That's subjective @RangerGeek50. Fastest can mean just making random moves. Tang can play extremely fast and good (ultrabullet and hyperbullet), but I'd say Alireza and Magnus can play fast and extremely good (1+0 bullet).

All, mostly 1+0
Reza vs Magnus (alireza2003 vs drnykterstein + drdrunkenstein + manwithavan):
drnykterstein drdrunkenstein manwithavan total
alireza2003 M 201½-183½ R M 9-3 R (old) None* M 210½-186½ R (~53% M)
Reza vs Tang (alireza2003 vs penguingim1 + clevertacticbutfail):
penguingim1 clevertacticbutfail total
alireza2003 T 508-478 R(no TC specified) T 7½-4½ R T 515½-482½ R (~51.65% T)
Tang vs Magnus (penguingim1 + clevertacticbutfail vs drnykterstein + drdrunkenstein + manwithavan):
drnykterstein drdrunkenstein manwithavan Total
penguingim1 M 484½-233½ T M 156½-109½ T (old) M 2-1 T M 643-344 T
clevertacticbutfail T 4-3 M M 5-2 T (old) None* M 8-6 T
Total M 487½-237½ T M 161½-111½ T (old) M 2-1 T M 651-350 T (~65% M)
*May have missed some
OVERALL:
M>R
T>R
M>T
M>T>R
Magnus>Tang>Reza

The thing is... when Magnus wants to win he wins :)

I think Andrew Tang is the best hyperbullet player. The slower the time control gets the more likely Magnus will win against Tang. I think somewhere about 40 seconds is where Magnus takes over.

@ruzgar9543
Agree with you! This is what statistcs show and that is not possible to contradict, but as stated by a couple of viewers Tang is probably the fastest bullet player on this planet currently, that doesn't mean he's the best just he is incredible fast.

Last I checked here on Lichess, Magnus was rated number 1 in bullet.

magnus for sure