There are new column sizing options in Opus 12, but old formats should still work as they did.
What are you trying to do exactly?
If you want the same column setup everywhere, it only takes a few clicks, as shown here: Folder Formats: Quick Guide
There is also a format lock already on each lister, which can prevent the format from changing. You may have your columns set to auto-size, however, in which case they will be locked to auto-sizing, not to a particular size. But you can turn off auto-size if fixed-size columns are what you want.
In Opus 11, auto-size was a single checkbox affecting all columns, but in Opus 12 you can configure it on a per-column basis, as well as several new sizing modes. (The old one-click checkbox still exists as well, but mainly to maintain compatibility with old formats imported from Opus 11.)
The video the same page links to at the bottom also includes details on the different column sizing modes you can use.