I would like to hear about that Spanish option as well so please Kindly share some information about it if you have any. I talked with 2 tax advisors from Madrid last year and both confirmed me that as a trader, I would have to pay regular income taxes, in other words, up to 45% marginal plus social security. Companies in some circumstances enjoy a lower 15% corporate tax year in their first two tax years then it is the regular 25%. Dividend tax is 25% as well. Indeed Madrid doesn't charge any wealth tax but it's not a new thing, it's been like this ever since Spain decided to introduce the wealth again because in the past it has been totally abolished and if I remember it correctly, it was reintroduced after the financial crises but I'm not sure about this.
Check the thread below, there is a link to the spanish advisor, my understanding reading on the topic when i checked was there was a lot of wishful thinking in their interpretation, planned rather than implemented changes to the Beckham law. Tried to contact them but with no avail.
I'd understood the wealth tax in Madrid was also reintroduced during the financial crisis, but with a higher threshold, from memory 2 million euro for 2017 or 2018 and somewhat lower rates than in other parts of Spain. Understood while looking for updates it had been decided only recently to cancel it altogether for 2019. Big difference for me as at the moment most of my income is passive. Reading tax treaties, dividends and interests from some low tax markets where i have non negligible investments are 10 and 15% from the spanish side. Not bad, especially for a Madrid fan.
If you are looking for a low tax set up in the EU, again, check out Gibraltar, there are several set ups possible, you basically don't need any if u plan to live there and trade afaik, and there are only short stay requirements under the cat 2 investor program, but again if you are a EU citizen, plan to live in Gib and get your income from trading financial markets, 2 law firms I got feedback from confirm it would be tax free.
We went there last summer to check the place (second time for me in Gib, and a few more times in nearby Costa del Sol), not that bad of a place , wife and daughter who speak much better english than spanish keen on moving there this year, but I'll probably give it pass because sports wise there is not much for kids, whereas one of the most successful schools in western Europe for daughter is just outside Madrid, so it is another plus.
https://www.elitetrader.com/et/threads/trading-for-a-living-taxes-in-eu.318391/page-10
You can jump to halfway through the thread, to read more direct feedback from lawyers there :
https://www.elitetrader.com/et/threads/gibraltar.319989/page-4
To make it faster here are the links to the Beckham law related website :
https://www.spectrum-ifa.com/financial-advisers-in-spain/spanish-tax-201/the-beckham-law-in-spain/
https://www.spectrum-ifa.com/beckham-law-2018/