From your description of your use case, a super convertible ought to be a good choice. Let's figure it out.
As a general consideration, pic always help
First, the mower deck. The criss-cross blades are for finish mowing, for brush work you want the single heavy blade. You'll definitely want to remove the front guard, to let the crap exit and not clog. Don't remove the rear guard if you value your ankles.
All the supers came stock with governors. It's possible yours was removed, or is not functioning. You should see an aluminum roughly cylindrical thing about 6 inches long, under the left side of the fuel tank, with a pulley which rides on the fanbelt. If it's missing, you should be able to find one on ebay or at GT or Richard's. If it's not working, there's lots of info on here about how to repair/tune.
Re gearing, you want to be in low axle. Look for the stubby handle pointing down, under the right handlebar. Move that handle forward. That cuts the groundspeed in half. You can't use GRWs on a machine with the two-speed axle, but you shouldn't need to, because they serve the same purpose.
Let's stop here and see where you're at.
Keep those cards and letters coming, and