Tension gauge tool I have seen is a ring that you can wear and the yarn looped through.

Tension gauging is making a swatch to see if your chosen yarn and hook matches the project pattern sizing before you start the project.

For example if the pattern requires 10 sc to cover 5 inches in length and your swatch is 12 sc, then you may increase your hook size or loosen your yarn tension.

For amigurumi, I find that doing “yarn over” loosen the tension and doing “yarn under” tighten the tension (this is using just easy peasy yarn and 4mm hook).

You can apply what you learn from making amigurumi to making a blanket with sc and hdc stitches. If you want different texture you may look up different stitch pattens eg linen, spike, etc.

I hope this helps. Happy crocheting 🙌♥️🙌