The guitars are double tracked. But there is also some very slight modulation effect on them to make them sound wider. Probably an Eventide H3000 or something similar.
Billie was using Rob Cavallo's modded Marshall Super Lead amp for this song and the rest of the songs on dookie. As far as I'm aware there isn't a chorus effect on that amp and from what I've been able to find out Billie layered the guitars so there's often 4 tracks playing at once which does create that chorus like sound (he is a very tight guitar player). You can hear one set of guitars drop out at the start around 0:57 and come back in around 1:02
Hi , I’m a home producer, and I’ve been doing recording for a decade now I can almost guarantee with 99.99% certainty that this is a multitrack recording and nothing else 😊
