The likelihood of forming condensation on the interior surfaces of your garage are minimal, in most cases, if the garage is tightly sealed. However, if you are dealing with extreme weather conditions, or are generating elevated moisture levels in the garage, some condensation may be observed on poorly insulated surfaces such as window glass. Not the end of the world by any means.
What should be avoided is extended moisture condensing within the interior of walls as a result of poor insulation, poor sealing, missing vapor barrier, etc. Given the winter design temps of Iowa, I would have preferred to see a better wall insulation, but you should still be able to successfully heat your garage. If you see water pouring down the windows you should lower the interior temperature and/or reduce the interior moisture levels, and investigate if you have any large sources of infiltration.
Bear in mind that electric resistance heat has the same heat output regardless of configuration. The only more efficient unit is a heat pump, especially earth-coupled units for your area, which would make sense if you ever required air conditioning of the space. Since you make no mention of that I will assume that you are only in need of heating.
For electric heat there are several possibilities: Radiant panels or heaters, baseboard radiation (convection heaters), or fan-forced heaters.
Radiant panels are the typical choice for high-ceiling areas where you are trying to avoid heating a large volume of air. There are a few manufacturers, such as the Aztec brand, of 24"x24" radiant panels that may be suitable for your application, but I would rate this the least desirable option. Rapid heating of the space is difficult with these units, and there will likely be hot spots in the garage directly below the units due to the ceiling height. At a guess, I would think that your space would require at least six of these units, perhaps more for even coverage.
Baseboard heaters would get my vote for most desirable, though not without some drawbacks. Heating by this manner produces a very even (consistent) space temperature and is a simple install. The units operate silently except for an occasional sound as the units expand and contract. For shop use I would select a unit with a heavy duty cover. The drawback is that recovery times are not as quick as the fan-forced unit but I think that is not a killer detail. Just dial up the temperature a half hour prior to use.
Fan-forced heaters are probably the simplest and cheapest approach. The only complication are the framing requirements and the need for an unobstructed "view" of the shop for even dispersion of the heated air. Typically this unit would have the fastest recovery performance. They also have the highest amp rating due to the fan start up and would likely require a larger conductor. The drawbacks are the noise and the tendency to generate dust due to the fan. Additionally, the fan blades will have to be cleaned from time to time and the fan would have to be turned off during certain shop operations (varnishing comes to mind) which may involve hazardous materials.
All of these devices will most likely utilize a "line voltage" thermostat which should be carefully positioned and labeled as High Voltage. I always recommend a step down transformer and low voltage thermostat if available. If performing operations with hazardous materials be sure to provide intrinsically safe electrical devices to avoid sparks. Always exercise caution when working with high voltages, particularly 208/240 volt.
During periods of extreme cold, reduce the interior temperature accordingly. For example, at 40 degrees outside temperature you should have no problems with a 70 degree interior temperature. If it is zero degrees outside however, a more reasonable occupied interior temperature might be 60 degrees. All depends on your particular application.
Hope this is helpful.
As always, offered only as opinion
