About lug nuts only: having and using a torque wrench is not enough. You have to also use it properly. I once wanted to torque my wheels to 120 or 130 Nm (the correct torque is 110 Nm, I remembered it incorrectly). I also looked at the incorrect scale in the torque wrench, torquing them to 120 or 130 lb ft. That's a helluva lot of torque! No damage was done. It did feel a bit strange to torque them to such high torques due to my good muscle memory, but I blindly trusted the incorrect scale on the torque wrench and torqued them tight anyway!
There's a huge safety margin in wheel lug nuts. If you have any kind of muscle memory, just use the same lug nut wrench and torque to approximately the same torque they originally had. That will do in most cases. If it's overtorqued by 20% or undertorqued by 20%, it won't fail.
This year, when changing the winter wheels to summer wheels, I first torqued with a lug nut wrench, then checked the torques with a torque wrench. They were very accurately torqued due to my good muscle memory. I assume the accuracy was about 15% or so.
Note, my answer is only for wheel lug nuts. Other fasteners may not have such a good safety margin in automotive applications. So, if you need to remove the caliper bolts, I would go ahead and purchase the torque wrench. And if you are going to purchase the torque wrench, why not check your lug nut torque with it anyway?
And oh, if at all possible, avoid the clicker-type torque wrenches that should be periodically calibrated and select a beam-type torque wrench that won't go out of calibration (apart from perhaps needing to be zeroed properly by bending it, if heavily damaged). It's slightly less convenient (you need to look at the scale from a particular direction orthogonally). However, the beam-type wrench is actually the mechanism that is used to calibrate the clicker-type wrenches! Not only that, but also the beam-type wrenches are cheaper.
Of course, in tight spaces the clicker type wrench may be better, so you may want to purchase both. Brake jobs are not tight space jobs.