I also report lags. Not on all tools, but it happens.
On a brand new iPP M1 with 8GB of RAM, the first painting i did with ASP in this model, and without using swap space:
Screenshot taken today.
Maybe i can have an explanation for that behavior in my case. I explain:
First i installed some brush sets (the Indexes from Cladio and my own sets created by zero inside ASP), all work perfect and no problems at all.
Then i installed a very large Photoshop brush set; the Michael Adamidis oils&acrylics brush set. I installed the TPL version to preserve tool configurations. Unfortunately it created a single category for all 400+ brushes. I deleted many of them (there's way too many variations of the same brushes) until that group had around only 40 brushes and tweaked them (to use emboss features). It was a very long process, because it took me around 30 seconds just to select any brush; swap memory is used (around 1.5GB). When i finished, app speed seems back to normal, no swap used.
I restarted ASP many times, to refresh memory usage. Then i started to make my painting.
To paint i used this MA brushes group and the default Oil group. I was selecting constantly the 'send feedback' feature, and i never saw any swap usage, always the same as the above screenshoot. However, the lags and delays started after some time. Even restarting the app, sometimes the lags started in few minutes, not only tool selecting delays, painting lags too. The tool selection and painting algs dosn't seem to be selective, same brush may be selected or paint instantly or have intense lag.
The only thing i noticed is that it starts when i change to any brush from another category. Even using only two brush groups, as more i change between them, the faster appears the lags.
The only thing i can do for myself is to create new brushes replicating the ones from MA. Maybe they are too resource intensive, or maybe there's some hidden ABR/TPL resources in Photoshop brushes i don't know. However, technically no swap memory is used, and the problem may still be here.