A combination blade should work fine, just not something that is too agressive , but not a fine cut blade either, teeth will be too small .. I would think like a 30 or 40 tooth blade would be fine.. I would look for something with an ATB .. alternating top bevel if you can find it, that will make the cut finish smoother . the TCG , triple chip grind is specified for laminates and hard plastics, so dont think that is necessary for ploy being it is pretty soft compared to plexiglass..
I've cut a few Urethanes with the combo blades I use for landscape timber work with great results. The blades are thin kerf, 35 teeth, carbide tipped combos. Used paddle bits for the holes with no problems.
If you don't want to used a saw a "sharp" utility knife works great. I cut most of the edges that need to be trimmed with one, and use a speed square for a straight cut. Just flex the blade back a "little" when you cut. Spray some WD-40 into the cut as a lubricant. John