A few questions about a single user instance

I’m running a very small instance and I highly recommend using LCS:

https://github.com/Fmstrat/lcs

Essentially it automatically subscribes to popular communities from other instances on behalf of a user within your instance. That way, when you want to subscribe to a community at some point, it’s quite likely that it will already be full of comments already.

Posts will make their way over when someone interacts with it (comments/votes on it). I think old comments may make their way over under the same conditions. Old votes will not make their way over.

You can search for a post or comment to force your instance to load it (copy the federation link, the rainbow-web-looking icon) just like you would do for communities.

You can see posts from the past, but not comments.

I first used lemmy on lemmy.world but due to its size I had several issues of things just not loading and needing a full page refresh.

A lot of us did this, but now the big servers like lemmy.world are having to send every vote, comment, post to a huge number of servers and it results in unreliable delivery due to the servers being overloaded. There are 10 second timeouts in the HTTP connection between servers and the retry attempts are limited (and in their desperation to keep the severs from being even slower they are reducing retries).

The federation protocols have too much overhead, I don't see how this will work. I've been suggesting that Lemmy to Lemmy replication of comment/post/votes not even use federation and bulk download via polling the front-end API and even some new API calls intended for server to server message sync. An entirely new system.

Is having a single user instance realistic or should I try find another small instance?

You would be helping the Lemmy overload problems of servers like lemmy.world to not run your own instance and get on another small one that's already getting most of the content already.