Ferdinand II came to power at a time of religious conflict and Catholic resurgence. His son Ferdinand III came to power in the midst of a long war which had begun when he was a child. It is hardly to be wondered at, therefore, if Ferdinand III lacked the religious zeal of his father, or if he placed making peace at the top of his list of priorities.
Like many other rulers of the time period, Ferdinand was intellectually curious and talented. He was interested in painting and magnetism and was the first in a line of Emperors who composed music. He was present at the great victory at Nördlingen in 1634 and at the defeat at Jankov in 1645, but it is doubtful if he had much personally to do with either battle (General Gallas handled the military details in both cases).
Ferdinand III generally supported Trauttmansdorff’s program of uniting the Empire and strengthening Imperial power at the expense of some Catholic gains. He tried desperately, as had his father, to separate the French-Swedish alliance, without success. Ultimately, he was able to keep his authority strong in his hereditary lands, but had to give up hope of maintaining practical authority over the rest of the Empire, and he was also forced to make a separate peace from Spain against his wishes.
There has been no good biography of Ferdinand III for a long time, but there not only is one now, but it has been translated into English (from German, of course).