Hi,
I got a Ryzen 9 3900x, and for some reason Cosmology downloaded 24 core WUs.
I still need 1 or 2 cores for GPUs.
I saw I can set the CPU count to a max of 8 on my account page on this website.

Can this be updated from 1 to 100?
I would like no more than 22 thread WUs, preferably 16 threads or less.
Thanks,

That number is the max per work unit. Set it to eight and each task will use eight cpus. You will want to set no new tasks for the project and abort any tasks you have. I usually exit Boinc Manager and all running tasks and then open it back up again after making changes to make sure they get read. Once you allow new tasks, it should read the preferences and get tasks.

Yeah, but I want more than 8 CPUs.
The website doesn't offer this option.
12-16CPU WUs is ideal for me.
I can set it to unlimited, but can anyone help me in what I have to populate app_config.xml with?

(like name, etc...)?

camb_boinc2docker workunits set to use 4cpus run between 6 - 7 minutes on my Ryzen 2700. I really doubt you would want any higher than eight cpus. I don't know if the work units will even scale higher than eight. Attaching my app_config.xml if you wish to play around. Set to run 3 concurrent work units with 4cpu cores each.

<app_config>
    <app>
        <name>camb_boinc2docker</name>
        <max_concurrent>3</max_concurrent>
    </app>
    <app_version>
        <app_name>camb_boinc2docker</app_name>
        <plan_class>vbox64_mt</plan_class>
        <avg_ncpus>4</avg_ncpus>
    </app_version>
</app_config>

No, I don't mean 1 WU spread out over 12 CPUs, I mean 1 WU that's optimized for 12CPUs.
Apparently the 24CPU WUs are 1CPU WUs, locking in all my other CPU cores, so projects stalled overnight.
I aborted them all!

All you had to do was change the values in the provided app_config.xml

No!
I'm not even supposed to touch that!
Cosmology needs to make sure if they're sending 24 thread WUs, they actually work on 24 threads!

It's a problem in counting real cores versus SMT/hyperthreading. You can fix it by setting the project preferences to eight or less cores per workunit or you can use the app_config.xml method to see if you can get a 12 core or more work unit to complete.
I don't know of any of the Virtual Box projects that do what you want.

I will limit it to 4 cores at a time. As even with 8 cores I get compute errors.
I think because cosmology taxes the CPU more than most other projects, causing the cpu frequency to drop below the speeds it can sustain on a fixed overclocked frequency.

The more single threaded WUs I get from Cosmology, the lower the CPU frequency goes.
From 3,9Ghz on most projects on my 3900x, to 3600Mhz with 24 threads of cosmology.
One or two threads might allow the cpu to maintain the set frequency of 3,8Ghz (I hope).

The only reason why I overclock to manual, is because auto overclock (PBO), causes the CPU to ramp up and down, and causes the power usage to rise (power consumption drops at a fixed overclock, vs rises at a dynamic overclock), plus a fixed overclock allows it to run in higher boost (+50Mhz) over dynamically overclocking.