It's all about getting used to the bike.  Be familiar with it.

I ride z1000 with side boxes every day to work.
No issues when lane filtering through traffic jam with the kapchais.  99% of the time I'm able to pass through even through narrow space in between two cars without putting the foot down.  At times some bikers will give me a thumbs up.  Lol.

What I learn is that we must master on balancing the bike straight at low speed, even when the bike is almost at complete stop.  With this skill and confidence, every day ride through the traffic jam is no issues.

Need to practive more, the gap between cars in Klang valley when during Jam in avearge still have space for bike to move in between, different if you need to go through jam in Penang George town for example since its sidemirror to sidemirror wide...

Was commuting using an aircooled Murica cruiser (the one that will cook your balls when stuck on traffic) before with side panniers to KLCC and back then changed to boxer engine powered bike.. but now downgrade to a scooter  (For commuting purposes) after I found out cost replacing clutch of liquid cooled boxer engine expensive as f!$$! hahaha...

So not about the bike width when it comes to traffic jam, but more to conserve my clutchplates..