I can scroll through a page of >1000 movie cards and there's no choppiness or lag at all in the webUI. The cards have blurhash placeholders until the actual thumbnail loads, which is always very quick.
Swiftfin for the Apple TV is admittedly very barebones and can be choppy when scrolling through big lists, but it has never lost pairing or failed to load anything for me.
New media shows up pretty much immediately for me. Did you disable the "real time monitoring" setting in your libraries? Jellyfin will use something like ionotify or whatever your platform/fs supports when it's enabled.
"separately configure tiles to be rendered" is one checkbox, assuming you're talking about trickplay images, which was a recently added feature and I think is enabled by default for new installs.