How to define plecs circuit (blockset) simulation params separately from the main model?

As I understand, to get the best performance I need to simulate the plecs circuit in variable-step mode. However, it seems that I can only make global changes to the simulation setting via the Simulink Simulation Settings dialog. I want to be able to do this because I have some models that run in plain simulink that would work much faster with (and are designed for) fixed-step simulation. Is it possible / desirable to have plex solve the circuit with a variable time “within” the fixed time of the simulink circuit?

This may sound like a convoluted question, but I am relatively new to plecs - although I have worked on models made by others in the past. I am using Plecs blockset (4.5.4) with Matlab 2019b on Windows 10.

For most applications we recommend a variable step solver, but PLECS Blockset works with both variable step and fixed step Simulink solvers. Note that you can have fixed-rate periodic tasks and a variable step solver. Variable-step solvers still accurately take simulation steps at the discrete control time steps in addition to the adaptive time-steps due to the power electronics system dynamics.

Also, if you are using a variable step solver and the simulation is running slow, check if you should be using a stiff or non-stiff solver.

Simulink also has a “local solver” configuration which you may be able to use, but you should refer to Mathworks support for documentation on that feature. I am not sure if it will be applicable here.