The worst film curving and curling I know of is when desperate students adjust the humidistat on the film drying cabinets in effort to get their negatives dry more quickly. One student will find their negatives had been caused to curl by another student cramming 15 hours of work after 2 am to have dry-mounted fiber prints for an 8 am critique. Argument ensues. Accusations fly. Someone gets drowned in the print holding bath. All because of removing moisture too quickly from the film...
Last month I used and developed 5 rolls of Neopan 100 Acros that I bought in 2013 (they expired 2015) and the tight curling made them NASTY to work with. Loading them onto reels for developing tested my ability to stay rational in front of my dog who thinks I'm a good person except when my arms are inside "the black bag".
I am donating my remaining expired Acros. Will never touch expired Acros again. Expired Acros can be recycled for all I care.
My FP4+ negatives are gangster flat when I pull them from their glassine sleeves. When I go to work with one, I smile at how handsomely heavy it seems, with gravity helping the ends of the strip bounce so the emulsion glints its graphite-shine in the light - they're my most breathtakingly flat negatives.
Of low-cost films, I remember trying rolls of Kentmere and not having curling/curving issues.