TC,
The tool of preference for most door hangin' pros is the planer. OTOH, check the Journal of Light Construction Finish Carpentry forum and you'll find several who use circular saws. A guided saw, especially a Festool guide saw is by far the best option among CS's. Of the Festool CS's, the TS75 would be a better choice than a TS55 because of it's power and depth of cut, but the TS55 will work also.
Regarding what Festool products can and cannot do... In other forums, I've read many posts stating "facts" about the limitations of Festool products, and especially about cost versus value. In the vast majority of cases, the poster had never used them!!! He/she was simply regurgitating unfounded opinions or marketing hype put forth by vendors of competitive products.
Regarding cutting narrow strips... I ROUTINELY remove 1 mm from board. No biggie. Line up the guide rail, clamp it down and cut.
Regarding accuracy... Last year, I had to sister the joists in my garage ceiling with 14-18' 2X12 Microllam beams. Unlike standard wood joists, Microllam beams are closer to true size. They were 1.75" thick and about 11.75" tall. Also, they are very tough buggers. Each one had to be trimmed to fit - cross-cut and ripped. Using my lowly TS55 and a Panther blade, I ripped some of the Microllam beams their full 18' length using two joined Festool guides. They result was that they were straight within 1/16" over the full 18' length.
Suggestion regarding Festool tools and Festool saws in particular: Actually USE THEM before making definitive statements about them. Don't assume that your experience with other, non-Festool products is any indicator of Festool advantages or limitations.
Dan.