I have been using my Notes only sub-vault on mobile for some time, and it has been fine. Thanks to Remotely Save plugin syncing to my Nextcloud in Webdav mode, there has been a very minimal amount of conflicts early on. Then I figured how to configure it properly. So, it was user error.
It has been a breeze since. The only minor annoyance I have is the common plugins’ configurations cannot sync automatically. That is still not a headache since the very limited count of plugins on both sides, and how rarely I change those settings. If I do change some setting, I just make a reminder task on my one device to remind me to make the same change on the other device.