Mike is correct there: GA4 is not worth using and judging from the number of bugs and absent functionality, it's not likely to be a worthy tool for another year or two. Many companies think to do double tracking, but even this is not worth it at the moment since how we do tracking for it may change too.
Generally, parallel GA4 tracking implementation in GTM depends on how your UA tracking is implemented now. If your current implementation is trivially linear (each event takes a tag and they don't reuse variables for categories, actions and labels), then yes, you will generally have to make a tag for every tag if you want to maintain the linear structure.
You could do it smarter, having a custom JS variable (or a lookup table, depending on a situation) generating the data for your dimensions depending on what has occured. In the latter case, it may be ample to have only one GA4 tag that would use a lot of existing triggers. But that requires quite advanced GTM and JS knowledge.