Are these funny anti-Trump shirts or serious ones?

Both. "86 47" and "A Photo Op Is Not a Policy" are dry; "A Bully Is Not a Leader" is plain. Every product title says exactly what the shirt says, so you can pick the tone.

Can I wear an anti-Trump shirt to vote?

Rules vary by state. Most ban candidate names and party apparel inside the polling place, so pick something from the voting collection for election day and wear these everywhere else.

What shirt are they printed on?

The Comfort Colors 1717: garment-dyed, 6.1 oz ring-spun cotton, relaxed unisex fit, true to size, with a soft direct-to-garment print. The hoodie and sweatshirt are the Gildan Heavy Blend: 8 oz cotton and polyester, unisex S to 5XL.