Putttn,
I have the ATF 55. for nearly all of my woodworking, there wood be absolutely no need for the TS 75. i have even worked with 2x lumber. I don't recall if i tried tilting at 45º with 2x lumber, but I have gone far enough into som 3" stuff that it was easilly finished off with my handsaw (one of those funny named Japanese saws with two sided cutting and thin kerf.) you have mentioned your age. believe me, if you are not already looking at the weight factor when buying hand tools, you will be very soon. i was very tuned in to tossing 85 # concrete blocks, 96# bags of cement, soaking wet, concrete coated lumber that drove the ankles 3"s into the gronud and the knees into the chin, and even heavier rocks for over 40 years, and believe me, i am NOW, very weight conscious. Unless you are expecting to work with very heavy (thick) lumber, I am pretty sure you will get along fine with the TS 55. it has plenty of power for most operations. you can always upgrade. (Be aware that you are already showing the very worst symptoms of Festool Mania for which there is no antidote. Proceed with extreme caution!!!) In my own case, i still have my old reliable Milwaukee that does get called in to service upon rare ocassions. If you want to know how I would proceed, knowing you are very limited for space and only just getting into Festool system, i would get the TS 55 and then start thinking about the Trion PS 300. The trion can span the deeper cuts occasionally needed and also can take up the slack to not need a bandsaw right away. I have both and use both. if i had to get along with BS or Trion, only one, i would keep the Trion. (I could use the extra space, but then i would probably get serious about the Kapex. See what i mean about no known cure)
Tinker