Since Germany is a mix of public health insurance and private insurance next to each other, we can see this. Normal employees are required to pick one of the official health insurance companies. Their families can join at no extra cost. They pay a fixed percentage of their wage income, their employer pay (roughly) the other half, it all goes into pool, so the healthy Clients pay for the others. No individual assessment, no lifetime caps.
But if you earn above a certain amount; are self-employed/ free-lancer or a state official (Beamte) - then you are exempt from the requirement and can choose to insure yourself with a private Company. This is then an individual risk assessment, and your rate is not based on your income, but a fixed amount. If you want your Family insured, too, each Person costs extra. The older you get, the more expensive the rates become. (The private companies do a lot of Advertising to get Young People to Switch by telling them how low their rates are compared to mandatory insurance - but Keep silent about how difficult it is to Switch back and how they can get in old Age when Money is low).
Small-time free-lancers often go without insurances because it’s too expensive, until they Need healthcare, and it bites them in the ass.
State officials are mostly private insured, and at first say how much nicer it is to get preferred Treatment. But it’s a huge paper hassle because for every single Thing, the doctor or Hospital sends them a bill, then they have to fill out a form for their health insurance, and another for their employer (who refunds up to 70% of the expenses). They have to pay the bill quickly, but the re-imbursement can take 4-5 weeks.
(In both cases, fraud has happend, that is, doctors/ hospitals billing for Services not rendered or billing for more expensive things. Some Claim that if the Patient sees the bill before passing it on, this would be prevented; but a) getting a copy of the bill could also be done with legal insurance b) legal insurance is already a complicated Point-System with abbreviations to the code book of approved Treatments that I doubt many patients would figure out billing fraud if cleverly done).
This https://www.tk.de/centaurus/servlet/contentblob/589226/Datei/1717/TK-brochure-welcome-to-germany.pdf is a bilingual PDF explaining the German social System from the POV of one health insurance (TK). Not in Detail, but for new arrivals.