Gibraltar is the holy grail, bar none, for the aforementioned reasons providing you have an EU passport. As for cheap, it is not cheap, the yearly overheads will be £50-60k minimum, not to mention you need a £2m net worth to qualify.
What defines "semi-hidden"? That is frequently mentioned on the forums, what does that even mean? This should be obvious given the cost, but don't work a regular job in the EU and you won't be on the radar. Owning property, leasing property, or having kids in a boarding school does not trigger any tax authorities to audit whether one is a tax resident︀ or not. Owning a car does not either, purchase a car and register it to︁ a company in Andorra with temporary MT plates to avoid VAT and having an EU︂ registered car. The most common reason anyone is ever audited, is that most people with︃ EU citizenship lived in some high-tax EU country for a long time and claim they're︄ no longer tax residents, but still live there full-time, or their country like some horrible︅ countries in the EU, Finland for example attempt to tax those that leave for number︆ of years after they leave.
If you're a Gibraltar cat 2 resident, there is no︇ minimum stay requirement in Gibraltar. If you're an EU citizen you can travel to the︈ EU freely without any visa or any maximum stay limitation. You technically must register as︉ a resident after spending 90 days in an EU country even as an EU citizen,︊ but this is not enforceable, there is simply no way for any EU country to︋ know you've been there for 90 days due to freedom of movement. Furthermore, nobody, absolutely︌ nobody, is going to ask you, an EU citizen, at an EU border (the gates︍ are all automated) where you're a tax resident.
For example, Polish citizen with Gibraltar cat︎ 2 residency buys a house Antibes, France thru a company and spends 4 months there️ in the summer, while spending the rest of his time in London as an example, but doesn't spend anytime in Gibraltar...