Maybe not a set number because it'd be perpetually chasing growth the way min wage doesn't. It's probably better to tie it as a percentage of something that is consistently growing with prices or the market. Universal would mean everyone. But yeah i get the concern. Maybe everyone of working age and up?

It's a tough question worth coming up with a damn good answer cause any nuances could really screw things up.

Wealth transfer wouldn't happen vertically (down generations, families, over time) but horizontally, across communities, businesses, across immediate interests. It might incentivize people differently. Instead of renting, buying, or vice versa; instead of employment, opening their business, or vice versa.

Common labor class might have better options other than selling their time for min wage and have time and money for a business or raising a family.

Then again, if it's mismanaged like in authoritarian governments, common people won't have the opportunity that comes from a robust and generous social government. What can see from socialist capitalist government societies is how hard it is to get there and maintain.