New to all of this and looking for some solutions. Not the most knowledgable so be kind. I am typically a sony a7iii shooter. I was working on something a little bit more important and rented an a7siii. I shot all day in 422 4K 120fps and my computer refuses to edit well with it. I am running a 2020 iMac with the 5700XT with 16gb of VRAM and have made proxies of the footage for editing with no luck. I occassionally get playback if I render the timeline but even that is hit or miss. Thanks in advance.
You'll get some suggestions to use proxies for such footage as I wouldn't expect Premiere to render that out in real time on a good day with the very best computer on the planet. 120fps at 4K is a lot of info to process and playback of footage isn't Premiere's strong point. If you downgrade the footage to a much lower resolution then you'll have more luck I believe. Tons of posts on that subject here so I won't rehash it all, do a search and your brain shall fill up quickly on the subject