When updating 2023, is it best to "Update All" from the Installed Packages or download & install the Core Server first?

I'd download the update from the admin, then run it on the cmd line, more reliable. Once that's installed and you're restarted, see if it still thinks there are packages to update.

do what ever backup routine you have , stop the server, use command line, update the server, start the server , pray to your adobe gods all as it should be

Just to confirm, I can to straight to update 11? I don't have to step through each one.?.

Only need to install the latest, they're cumulative.

On the flip side of testing each patch, if there is a breaking change, you can roll back to the previous patch—read the notes and then correct the offending pieces of code before performing the next update.

TBH, this is a new server that we're migrating to, the migration process got paused (hence the big gap in patches). Just trying to bring the server back to the latest and greatest and then we'll test our code migration.