Tile – the right way/tool to remove this tile and thinset from a concrete slab

Easy, no. It's a dirty, dusty, hard job.

I have used a 7 1/2inch circular saw fitted with a diamond blade. Shop vac, dust mask, fan in window (box fan fitted with furnace filter does wonders)

I set the depth of the cut to be just the thickness of the mortar and try to cut vertically along each stud. Depending on your helpers back strength, I'll cut horizontally at 2 to 3 foot intervals.

Pry each panel off (large crowbars or flatbars) usually its held together with a metal lath (wood in older homes, pre 1940s). Watch your toes, each piece will be 20-30 lbs.

PS leave the first row removed laying on the floor. It will absorb the fall of any dropped pieces... Nails holding the lath will act like hinges then let go at inopportune moments.

Shower tiles are not a place to cut corners. If they are porous then you will have a host of issues. Basically you will breed mold faster and the tile install won't last as long - mold gets in cracks and pops tiles out or at least loosens bonding. You need to get a non-porous stone, plastic, glass, or porcelain.

If going with 12x12 tiles you will need at least 1/16th of an inch given they are uniform - and perfectly cut 12x12 are not cheap. So you are looking at 1/8-3/16. Which means you need sanded grout.

For cheap I suggest you go on craigslist or whatever is equivalent locally (even try job leftovers at tile store). The bottom 3 feet of your install needs to be a good tile - you will need about 34 sqft. You can get decent porcelain for $2 a sqft and even cheaper if it is a job leftover or end of stock. You can still use your ceramic up top. And when switching tiles I usually put in a narrow trim of glass mosaic in between - will need 3-4 sheets.