It's super easy to self host (assuming you're familiar with docker), doesn't take too much server resource, and will give you access to features normally gated behind bitwarden subscriptions. Way better then the official self-hosted version. The main disadvantage is while it's open source, the code hasn't been audited yet, which might be a deal breaker for people obsessed with security.
Yeah I read it’s a bit double edged but would anyone ever want to audit a open source software that can
Take over a paying one?… might just take the jump.
It's actually starting to get common for open source password manager to get audit, often free of charge by a security company. Whether the project actually compete with a commercial project doesn't seem to matter. KeePassXC was recently audited for example: https://keepassxc.org/blog/2023-04-15-audit-report/
KeePassXC doesn't do any cloud syncing stuff. If you want your vault to be available on multiple devices, it's up to you how to achieve that (e.g. by putting the vault database file inside dropbox/gdrive/nextcloud, etc). Some people prefer this approach because they don't trust centralized vault services.
1Password and BitWarden are competitors and offer largely similar services (e.g. syncing your vault across all devices you own). BitWarden paid service is cheaper though, so it's more popular. Note that bitwarden free account is already good enough, the paid service offers some convenient features which actually pretty nice to have though, such as storing TOTP data in your vault.
VaultWarden is an alternative implementation of bitwarden server. If you're into self-hosting and want to host bitwarden vault on your own server, you can install it in your own server. It implements almost all bitwarden features, even those that only available in the highest subscription tier.