If you are testing the difference between paired samples I suggest you use a paired t-test.
If you have the time I can also recommend the Decision Making with Data module in JMP's STIPS course. (Personally, I found the experience of doing this course highly informative.)
With regards to the TOST, if I remember correctly this is more adequate for a situation where you have one mean value and want to compare it to an upper as well as lower limit. This can be useful in situations where you want to compare, e.g., the mean of a process output to a minimum and maximum acceptable limit. These limits are than tested pairwise against the mean, to see if any of the limits are not statistically different from the mean.