I'm very familiar with this process and have a Portuguese immigration attorney (and am actually in Portugal at the moment). First, residency indeed does not equal citizenship; you must be resident in Portugal, under the residency terms of the visa, for five years before either applying for permanent residency or for citizenship. Obtaining citizenship requires passing a proficiency exam in the Portuguese language. The benefit of the Golden Visa is that you are only required to be in country 7 days a year. If you can be in the country long enough to be a "tax resident" (183 days, I believe) then a visa like the digital nomad or passive income visas are far cheaper and faster to obtain.
Second, Golden Visa investment requirements used to vary based on where the investment is made or to be used. Lisbon, Porto, and the Algarve, amongst other high-demand locales, required the maximum €500k whilst more rural areas allowed investments as low as €330k (IIRC; actually lower than that for some qualifying real estate investments for properties of a certain age). Now, real estate investments are basically out, including funds - as is the direct capital transfer option. You can still invest €500k in other types of funds or scientific research, or create a business employing 10 full-time people for a minimum of 5 years. The cheapest option is a donation of €250k into an approved arts program - but this is a donation, not an investment. I think only a handful of people have gone this route.
If you're actually planning to move to Portugal, the Golden Visa probably wouldn't have been the best route anyway - it's really best for those who want to start the process but can't yet relocate.
Boa sorte na sua busca!