That's not the only situation where there are delays when browsing sounds:

When adding another part to a performance (not in Pattern Mode), I noticed a delay when switching sounds in the category view.

You are right

I hope in some solution

I'm not sure what "normal way" means. If the GUI seems sluggish for any actions - turn off screen animation. It slows things down.

Not performance - but also turn off blur - it obscures relationships between different GUI elements because there is background bleed to foreground color which can confuse what the GUI is trying to "tell" you about relationships between parameters.

I have beeps turned on - I'm not sure if they slow anything down. But you can turn those off too if beeps don't help your experience.

The main thing is to turn off animation. You may already have it off. Turning off animation turns a turtle into a horse - not a Ferrari.

As you scroll through "sounds" - you're able to preview/audition the new sounds - so this loading and unloading takes some cycles to shuffle data. It's better than it once was.

The "normal way" is simply browsing through sounds in the main Category Search page - not in pattern mode or when adding a part. Try it and you'll see. The lag is likely due to a heavier amount of TG reconfiguration (merging performances vs simply switching the entire performance).

It's a bit reminiscent of the RM1x and RS7000 and probably other Yamaha synths with similar TG engines: if you were switching songs, the more different the voice setup, the longer it would take to switch. Of course the SWP-70 TG processor is generations beyond those.