Its an impressive graph view but I wouldn’t consider 400 object large, specially with just 15-20 lines of information in each object. I would hope anytype doesn’t suffer performance. 
Starting at 10.000 objects or more I would consider it large and it should still not suffer performance then (or even higher 15.000 or 50.000).
If I look at my intended usecase for Anytype (or other note taking apps) I use it for daily notes (365 notes/year), my collections (movies (1000+), games (1000), Lego (100), etc), inspiration boards (500), life organizing (250), inventory (1000), etc.
This will quickly ramp up to 5000+ objects within one or two years if Anytype would become my daily driver which at this moment it isn’t for obvious reasons being so early alpha. 
So I hope that Anytype does get tested in the 10.000 or even 100.000 objects and still hardly suffer any performance!