This trip goes through remarkable places, I was lucky to experience quite a few without ever doing such trip in that location.

Uyuni salt plain - magical experience, better than any photos. Climbing on old rusty train cut into chunks, jumping between wagons. Or sleeping in salt-cubes-built iglu. Or hiking to 5200m high volcano Tunupa just next to salt plains.

Sucre - nice colonial feel.

Potosi - evils of colonialism in plain sight. Hard place to swallow. Also possible to go to one of hundreds mines in the famous hill where all the silver mines are. There can be some nasty sillica in the air, beware. But mines look like you would expect in 3rd world - basic, dangerous, and a stick of dynamite is never too far. If you want to see effects of high altitude on fertility, local church is a (traumatic) place to visit.

La Paz - proper high altitude capital, don't be surprised to feel dizzy when stepping out of plane at 4100m altitude.

Copacabana - I presume the one on Titicaca - recommending visiting Isola del Sol, talking to locals. Never had a frozen beer in pre-frozen mug, when outside was -10C and even inside barely 0C, even the foam froze so had to be chewed.

One thing seemingly skipped since this was more just a regular travel path - you can ride down on a rented bike Camino de la Muerte near La Paz - or Yungas death road. In 1 day, you bike from 4700m high frozen planes down to tropical jungle, on shabby muddy roads cut to properly vertical slopes, with waterfall falling down your neck. Don't skip this, even if you are not a seasoned biker. One of those memories for rest of the days.