I just read through the full thread here, and it seems like there was an issue where processes belonging to other profiles were lingering around a bit too long. But now that no longer appears to be an issue, correct?
“That other issue where it opens in a closed profile doesn’t seem to be happening anymore, but the HUGE memory issues is very very bad.”
In order to better assist you with memory-related concerns, we need to establish a base-line measurement of how Brave performs on your system. The best way to do this, as shared by @clifton earlier, is to run a fresh profile (with no extensions installed), and monitor the performance of the browser for a bit.
Standing up a new profile can be quite a bit of work, however. For now, would you be able to share a screenshot of Brave’s internal Task Manager (☰ › More Tools › Task Manager)? You can enable additional columns of data by right-clicking any of the column headers, and choosing the desired data types from the resulting list.
Here is my own task manager, from Brave Nightly, for example:
Note how the browser itself has an entry with its own memory figures. The same is true for an installed extension (MetaMask in this case); it too has an entry with its own memory figures. Additionally, note the Profile column which tells me to which profile the process is associated.
A similar screenshot, showing the same columns, would be very helpful.