Help - Live Set with only 10-15 tracks is causing massive CPU slow down. Cant get anything done - can anyone provide some insight?

I recently purchased the Output VST bundle and I love it. Amazing and inspiring sounds. Was working well until i started getting to about 15-20 tracks. Now, when opening the set, my entire computer goes into dinosaur mode. Can hardly do anything without getting the spinning wheel. Even turning on and off my mac screen is a struggle. But if i close the set, open a new one, everything’s back to normal. That is until I start getting to 10-15 Kontakt instruments up (all output).

I’ve read a lot about freezing tracks so I have done that on about half of them, but i can hardly even do enough with the set open to even accomplish that. I know flatten will help even more (but i’m not sure how much more) and Id like to avoid flattening and committing to each track. If this is my only option I can work with it but i’m not sure that’s the case.

I’m new to music production and things we’re going really well until this has put a complete stop to my work. Any advice is much appreciated. I can’t find any Output advice on similar situations, it’s a good product that I can’t find many bad reviews on. I have completed batch re-save for all VST’s.

SPECS: Imac brand new, 3.6ghz intel core I3, 8GB ram, 1TB. I am praying this isn’t just a RAM issue. I just bought this f*cking mac for this purpose and after doing lots of reading, I saw everywhere that 4GB is low and 8 is recommended. Even output says 8GB should work just fine.

Thanks in advance to anyone that can offer advice - I’m just stuck.