You can set up a TS to make perfect miters but you need to make a jig for best results.
I have a beautiful Delta Unisaw that I have had for 25 years or so. The miter that came with it wiggles in the slot from side to side.
So no matter how much I fiddle with the fine tuning adjustments it's almost impossible to make a perfect miter.
So I made a sled, I made the runners out of plastic from an old cutting board my wife was throwing out.
You know the white plastic stuff. I cut a bunch of strips at one time so they were a slip fit with some resistance.
I screw them to the bottom of my sled which is just a flat piece of plywood, I like Baltic Birch to make this type of jig.
Then I take a block or two of squared up wood to make a fence depending on the type of fence i need.
Using a known accurate tri square or protractor I lay out a line at whatever angle I am looking for on my sled measuring off the tablesaw blade.
Then I screw one end down with a drywall screw short enough not to mess up the table. Keeping to the line I put a nail in to tack the other end and make a couple of
test cuts. I put the two pieces together to make sure I have a 90 degree angle, once I am sure it's exactly correct I screw the other end down, if I need to adjust I pull the
nail out a bit and swing the fence to adjust it. Now you have a dedicated jig for whatever angle you need.
Here is a trick to glue your miters together without clamps.
Get yourself some brown craft paper, you know, the stuff paper bags are made of.
Slather your glue on one pair of the miter cuts, press them together on top of a piece of the craft paper on a flat surface and press together for a few seconds.
Get yourself a wet rag and wipe all the excess glue off right away, don't be shy about getting the wood wet.
Repeat for the other joints and go play golf or something while your waiting for the unit to dry.
What happens is the brown paper acts as a clamp as the cellulose absorbs the glue and holds your pieces together. After its dry just sand off the brown paper.
If you wiped off all the glue thoroughly you will not have anything to clean up or mess up your finish later.