I think these limits are server side. See these config options, for a project.

<max_ncpus>N</max_ncpus>
An upper bound on NCPUS (default: 64)

I can imagine that most projects didn't increase this from default so you are correct.

I do what you propose which is run 2 clients on the same PC, you have to take care about the memory usage, since both clients think they have all the ram, so if your pushing the ram limits then you can end up with very slow computer.

I'm not sure if the limit is 1000?, it should be 64x<max_wus_in_progress> N </max_wus_in_progress>, whatever the project configures N to be. Each project should balance this, as you say if they set it low then the users of project would be hammering the server for WU's so they need to increase it to lower server load.

I assume the client it's self has no limits. If you need more than 64 then you can ask the project admins to increase the limits to 128.

The client does have limits and once the server sends you over 1k tasks then you'll get a 'too many runnable tasks' message. Some people at SETI run an over version of the client with these setting raised to cope with the weekly Tuesday maintenance. You could try that, recompile yourself or run multiple clients as suggested.

I took a client and set the project to "no new tasks" and then suspended all WUs. Went to the cc_config file and set ncpus to 128 and then re-read the config files. Messages in the log indicated that the 128 CPUS had been accepted. I assume, based on the fact that the client didn't complain about the number, that it would accept that many CPUs.

The 1000 limit should probably be raised since computational capabilities are becoming so large today. Setting it 2000 or 5000 would probably suffice for many years. There are Talon systems out there with SMT4 or SMT8 settings that bumping close to 176 threads (44 cores with 4 threads). Seems like it would be an easy fix by either setting a variable to a new value or updating a comparison statement for the new value. Doesn't seem like a lot of developer time to me

Edits to cc_config will need a client restart to pick up the changes. I haven't done it before but I think you would notice the change on the host info displayed at project websites.