i've found the copy to account feature often fails if a dependency is necessary, so I try to pre-copy any major dependencies over like roles, custom records/fields, etc. Workflows often are also a place where I'm prone to using an "Account specific value" as NS calls it, like a condition on if a certain employee is the current user or something like that - those could be causing the error. But regardless you might have to open a case to find out the details of what exactly your error is from

I'd love for it to just work, but yeah - I have found that to be true. I have some very complex workflows that I need to move to a new instance, and this feature... could save me hours of time, but I'm afraid I have to choose between hours of recreating workflows or hours of dealing with NS support who will just tell me to recreate workflows.

Copy to Account is based on the underlying structure of SDF - though it's pitched as part of SuiteCloud, i've found it doesn't actually require any coding/suitescript knowledge to use it. It's not perfect/i still had a few unexpected error messages when copying over an entire account from SB to prod, but the error messages are generally much more descriptive and you have a lot more control. Could be worth looking into, there's detailed instructions in SuiteAnswers for setting it up

I'm working with a developer on a push to prod right now using SDF - much better than bundling

yeah i've been pretty pleased with it for prod pushes as well - it's not 100% perfect (e.g. it doesn't include reports, so those still have to be bundled or manually copied over) but wayyy less stressful than bundling where you might overwrite tons of fields/manual copying where you're hoping you're not human enough to make mistakes.