I just updated PP and After Effects and now my dynamic link is terrible. If I ALT-TAB between them, it takes 20-30 seconds for the Premiere timeline to update. I also updated my Nvidia driver to Studio. It's still awful.
are you saying you have after effects and premiere open at the same time with the ae comp open in ae and you're making changes in ae and when you alt-tab back to premiere that's when it takes so long to update?
Might help if you tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card and your source properties and sequence settings.
does it always take a long time to switch between the programs or only after you've made changes in AE? I'm assuming the h264 footage is 4K. That's a nasty format that requires enormous computer firepower to play. You might try transcoding to something like prores. Also, I usually render out my ae comp in premiere and place directly above the AE comp in my premiere timeline. Might be worth a try to see if it improves your performance. You might check how the memory is allocated between adobe software and OS and other software in preferences: memory. And you might make sure no other programs are running... but gotta say in my experience, alt-tabbing between ae and premiere has been pretty quick. I've done a few very intensive projects with this workflow but not recently...