SPM tests in Spectrum are run on the device itself not in spectrum. Spectrum only reads the results and the only limitations would be those on the device itself. There are no real limitations on the number of test results that Spectrum can read.
So long as the device is able to manage the number of tests you require Spectrum should be able to read and display results of all of them.
An example as to the limitations that you might have on the device itself in terms of the tests could be how often are the tests going to run- If you have 200 tests and they are running every 5 minutes is the test going to run again in 5 minutes based on the values configured on the test and can the device run this amount of tests?
That would be where your limitations are going to be with 200 SPM tests.