At its core Simulation only requires the modeling abilities included in SOLIDWORKS Standard within part and assembly mode. Solid, sheet metal, weldment, and surface geometry should be all you need to do an analysis.
In fact, when you are running long simulations you should absolutely have the machine only using a SOLIDWORKS Standard and a Simulation Standard/Professional/Premium license. There is no need for the machine to occupy a license for Toolbox/Costing/Routing/etc. while it is just calculating.
You may want to talk again with your VAR and see what the rational is exactly where they suggest SOLIDWORKS Professional or Premium to go with Simulation.
I am marking this as correct answer before we have tried it b/c I have now gotten head nods from a couple of SW designers here.
Another question I have been asked is if Simulation Premium can be bundled with SW Standard or SW Professional (simply to reduce overall annual maintenance cost). That might be a question for my VAR, but I do put a lot of credibility in real world experience.
I am a VAR so my credible real world experience may be questionable.
I have not seen any instance of a Simulation license being bundled onto a SolidWorks Standard serial number. It may have to be a separate serial number if you want to pair Simulation with SolidWorks Standard.
It will work well with any SWX license type. I have been using the stuff approaching 20 years. The license type doesn't matter. As mentioned by Ryan, minimizing the other add in's does enhance stability in my experience.