Update the Low-VRAM docs.

Author: RyanJDick

docs/features/low-vram.md

@@ -28,11 +28,12 @@ It is possible to fine-tune the settings for best performance or if you still ge
 
 ## Details and fine-tuning
 
-Low-VRAM mode involves 3 features, each of which can be configured or fine-tuned:
+Low-VRAM mode involves 4 features, each of which can be configured or fine-tuned:
 
-- Partial model loading
-- Dynamic RAM and VRAM cache sizes
-- Working memory
+- Partial model loading (`enable_partial_loading`)
+- Dynamic RAM and VRAM cache sizes (`max_cache_ram_gb`, `max_cache_vram_gb`)
+- Working memory (`device_working_mem_gb`)
+- Keeping a RAM weight copy (`keep_ram_copy_of_weights`)
 
 Read on to learn about these features and understand how to fine-tune them for your system and use-cases.
 
@@ -67,12 +68,20 @@ As of v5.6.0, the caches are dynamically sized. The `ram` and `vram` settings ar
 But, if your GPU has enough VRAM to hold models fully, you might get a perf boost by manually setting the cache sizes in `invokeai.yaml`:
 
 ```yaml
-# Set the RAM cache size to as large as possible, leaving a few GB free for the rest of your system and Invoke.
-# For example, if your system has 32GB RAM, 28GB is a good value.
+# The default max cache RAM size is logged on InvokeAI startup. It is determined based on your system RAM / VRAM.
+# You can override the default value by setting `max_cache_ram_gb`.
+# Increasing `max_cache_ram_gb` will increase the amount of RAM used to cache inactive models, resulting in faster model
+# reloads for the cached models.
+# As an example, if your system has 32GB of RAM and no other heavy processes, setting the `max_cache_ram_gb` to 28GB
+# might be a good value to achieve aggressive model caching.
 max_cache_ram_gb: 28
-# Set the VRAM cache size to be as large as possible while leaving enough room for the working memory of the tasks you will be doing.
-# For example, on a 24GB GPU that will be running unquantized FLUX without any auxiliary models,
-# 18GB is a good value.
+# The default max cache VRAM size is adjusted dynamically based on the amount of available VRAM (taking into
+# consideration the VRAM used by other processes).
+# You can override the default value by setting `max_cache_vram_gb`. Note that this value takes precedence over the
+# `device_working_mem_gb`.
+# It is recommended to set the VRAM cache size to be as large as possible while leaving enough room for the working
+# memory of the tasks you will be doing. For example, on a 24GB GPU that will be running unquantized FLUX without any
+# auxiliary models, 18GB might be a good value.
 max_cache_vram_gb: 18
 ```
 
@@ -109,6 +118,15 @@ device_working_mem_gb: 4
 
     Once decoding completes, the model manager "reclaims" the extra VRAM allocated as working memory for future model loading operations.
 
+### Keeping a RAM weight copy
+
+Invoke has the option of keeping a RAM copy of all model weights, even when they are loaded onto the GPU. This optimization is _on_ by default, and enables faster model switching and LoRA patching. Disabling this feature will reduce the average RAM load while running Invoke (peak RAM likely won't change), at the cost of slower model switching and LoRA patching. If you have limited RAM, you can disable this optimization:
+
+```yaml
+# Set to false to reduce the average RAM usage at the cost of slower model switching and LoRA patching.
+keep_ram_copy_of_weights: false
+```
+
 ### Disabling Nvidia sysmem fallback (Windows only)
 
 On Windows, Nvidia GPUs are able to use system RAM when their VRAM fills up via **sysmem fallback**. While it sounds like a good idea on the surface, in practice it causes massive slowdowns during generation.