[Offline file] Offline mode significantly faster than online mode

Hello,

I'm starting using offline files as a way to keep a backup of my data
on a share. I'm disappointed to see that most of the apps run way
faster in offline mode than in online mode (seems surprising to me...
online mode should only be better than offline mode).

My understanding is that it's because (correct me if I'm wrong):
- in online mode, reading a file involves a check on the server that
the cache is up to date
- in online mode, writing a file writes to the share (so the data goes
over the network) and not to the cache.

I don't want to switch to offline mode because I have some data on the
share that I do not have "Always Available Offline" (because I have no
need for them on my laptop and because the size of my hard drive
doesn't allow it). If I force offline mode, I'm no longer able to
access this data.

Is there a way to make the offline file feature never use the network
(I mean use it only for sync) even when online? What I want is that
regardless of the share accessibility, reading and writing a file uses
exclusively the cache, and if the share is accessible, the sync
happens in the background.

Thank you,
Vincent