So I solved why > [t,xv] = sim('vdpol',tf,options); was returning an error of too many return arguments.
I found that "Starting with R2009b, the sim command was enhanced to provide greater compatibility with parallel computing. The improved single-output format saves all simulation results to a single object, simplifying the management of output variables.
For backward compatibility with R2009a or earlier releases, use the backward-compatible syntax:
[T,X,Y] = sim('model',Timespan, Options, UT)
[T,X,Y1,...,Yn] = sim('model',Timespan, Options, UT)
If you specify only the model argument, Simulink automatically saves the time, state, and output to the specified output arguments.
If you do not specify any output arguments, Simulink determines what data to log based on the settings for the Configuration Parameters > Data Import/Export pane. Simulink stores the simulation output either in the current workspace or in the variable ans, based on the setting for Save simulation output as a single object parameter"
This means I needed to go into Model Settings > Data Import/Export pane and UNCHECK Single simulation output since I had the arguments [t, vx] on MATLAB R2019b.
More information can be found on:
Hope this may help someone else.
