Earlier quoted context omitted.
Just been switching to beancount from ynab. Apart from minor annoyances it's so much more powerful. If you're up for some programming and customization it's hard to beat (your choice between beancount/ledger/hledger matters less).
Are you trying to import YNAB's budgeting philosphy into Beancount? If so, how? I've considered the same transition but was unsure how to handle having budgetary categories dissociated from physical accounts.
I haven't found an existing tool to budget in beancount so you'd have to write it yourself. Other people have successfully used Ledger's virtual postings (which doesn't exist in beancount) for budgeting though[0]. It might be a way forward for you?
[0]: https://emacs.cafe/ledger/emacs/ynab/budgeting/2018/06/12/el...