TT or 5th? There are pro's and Con's to each. Since you mention state parks, many state and federal parks do have a trailer size limit. TT's tend to be smaller than 5th wheels but there is overlap. When you pull larger trailers they pull more stable getting the weight up and over the rear axle. Look at a tractor-trailer rig. There is also more headroom in a 5th wheel. TT and 5r's come in just about any floor plan you can imagine.
Since you are looking for an office space you might look at toy haulers. The "garage" can easily be made into an office. There are TT and 5r's in "toy hauler" configurations.
In the end it depends upon how you want to use it, as to what you get. Since you don't have the tow vehicle yet I'd wait until you found your trailer and take those numbers when you search for a TV.
Personally, we liked the 5r's over the TT's and bought the trailer before we bought the truck to tow it. Since the trailer was the priority to us it made sense do it in that order.
Good luck....