Regular named stock vs the one with "ADR" when buying European stocks to protect money from USD losing value?

(It's also because I expect those specific stocks to go up a decent amount, but I got character limited in the title)

What is the difference between the regularly named stock, and the one with "ADR", when buying European stocks as an American living in the US?

For example, when I search the stock for the company "Rheinmetall AG" on my brokerage's (Schwab) site, I get these two results

**RNMBY - Rheinmetall(ADR)**

**RNMBF - Rheinmetall Ag**

Marketwatch shows Rheinmetall AG as being 932.80 Euros, which is close to the "$984.8 / 1 XOTC" being shown on my brokerage's site for the one without ADR. The one with ADR is only "$136.34 / 1 XOTC" on the other hand.

What is the difference? If trying to protect against USD value loss, which one does it make more sense to buy?

If there's a difference regarding fees too, I'm putting over $10,000 in each of multiple companies I'm investing in. Is it just one fee for each transaction, or literally every share?