Need help optimizing my RAM for After Effect, Good setup but bad results ?...

Hi ! So here's my deal : I'm a tool. Really I'm sure I choose something wrong or did something wrong, I can't grasp what it is, but I'm pretty sure it has something to do with the RAM.

I used to have only 16Gb of RAM and everything was all rainbows and sunshine (not really but it was managable), then months ago I switched ALL my gear, CPU, MotherBoard, RAM, NVME... I now have 32Gb, and oh my ! Each time I open a new project in AE the nightmare intensifies.

here's a comparative of my old and new setup

I often work in 4K but believe it or not, It was already the case when I had only 16gb RAM, of course my projects became more and more complex when I upgraded my gear, but now, even in the very beginning of a project, when there's not much going on in my timeline, AE use at least 96% of the RAM, I'm forced to close it to do anything else, even opening Chrome is a risk...

I've tried all the cache disk/preference stuff, my cache is located on another SSD while AE is on my NVME, my only guess is that I need more RAM with higher frenquency ? Will it solve my problem ? I'm unsure and also broke.

I spotted two offers, should I go for : 64Gb at 4000MHz CL18 (274€) or 128Gb at 3200MHz C16 (359,99€ ) ?

I'm also stuck with windows 10 cause I can't boot in UEFI I don't remember why but years ago I made some silly stuff with my SSD and OS and I'm kind of stuck in legacy boot, I'll try to look into this, don't know if it would help to switch to W11...

Thanks in advance and sorry for the very long and not very so well-good written text (I'm not a native english speaker).