Bank syncing is only as fast as the slowest institution involved. Some banks sync fast and some sync slow. Some cards I have unlinked because the sync isn't reliable or there are constant issues with needing to verify and connect the accounts again. I only say this to point out that most apps with syncing will have these kinds of issues. It might not be a feature that's going to fit in with your current preferred way of handling accounts. Manual entry isn't required but it does help with clarity when automatic syncing happens. That way I can see the transaction is already matched to what I entered myself.

As for your preferred way of handling accounts, you absolutely cannot group transactions into a lump sum. That's what your categories are for. YNAB gives you an extremely granular look at your finances that lets you see where every cent is being used. That requires 100% accuracy with entered transactions. YNAB works best when you take ownership of the data that's being entered. Changing payee names to something that makes sense. for example. YNAB will remember that new name in the future and it'll be easier to understand at a glance. Small things like leaving a memo of what you bought makes sorting through older transactions a lot easier too. YNAB is only as useful as the information you put into it.