Former IT union leader. It really depends on the union because every contract is unique to the bargaining group and employer.

Traditional blue collar seniority, set wages, and hyper specific job roles simply won't work in knowledge work. So there tend to be higher severance payouts in lieu of seniority promotions, pay bands with equity review instead of pay steps, and very flexible job roles.

I think a lot of folks see unions from their youth working in construction or service work, which have a lot of corrupt "company unions" which mandate hour caps and shit benefits for part timers.

Realistically IT workers with leverage like ourselves need to think of unions as contract insurance. You already have a contract, the collective agreement can be as broad as possible to allow the flexibility to respect individual contributors, while the pooled dues are put towards eventual contract enforcement.

My first IT job gave me quite a surprise when they ripped up my contract and said "so sue us." That's the day I found out how much a labour lawyer hourly rate costs. 10 years later as a union leader I started signing the sizable cheques to our law firms, there's always a bad manager somewhere causing a lawsuit...