For "How much do casinos pay out?", start with how the offer is built. A welcome offer is rarely one bonus. It is usually a package spread across several deposits, each with its own match percentage, ceiling and conditions, and sometimes with free spins attached. The headline adds the parts together, which makes the whole look larger than any single step. Taking the package apart shows what each deposit actually earns and what it asks in exchange.
Reload offers return after the welcome package, often weekly, with smaller matches and the same kind of wagering. Whether any bonus is sticky or cashable matters as much as its size. A sticky bonus can be played with but is removed at withdrawal, so only the winnings above it can be cashed. A cashable bonus becomes part of the balance once the requirement is met. The terms name the type, sometimes under another label.
Packages split across several deposits release each tier only after the previous one is claimed, and often only within a set number of days of registration. Later tiers tend to carry smaller percentages. Each tier normally has its own wagering requirement, and some casinos stack them, so an unfinished requirement from the first deposit blocks the second. Reading the tiers as separate offers, each with its own cost, shows which of them are worth claiming at all.
Every offer names a qualifying deposit, a minimum below which no bonus is paid. Some also require a code at the cashier or a tick in an opt in box before the payment, and a deposit made without it rarely earns the bonus afterwards. Certain payment methods, often electronic wallets and prepaid cards, are excluded from welcome offers in the terms. Checking the method and the code before paying avoids a deposit that quietly earns nothing.
Short answers
Why do no deposit bonuses have tight conditions?
No deposit offers give credit or spins for simply registering, so casinos pair them with high wagering, a low withdrawal cap, a short deadline and one claim per household.
Why does the opt in step matter before depositing?
Some offers only apply when a box is ticked before payment, and a deposit made without opting in usually earns nothing afterwards.
When does a bonus code need to be entered?
Some offers need a code at the cashier or at sign up before paying, and a deposit made without it rarely earns the bonus afterwards.
How does a match bonus with a ceiling work?
A match bonus adds a percentage of the deposit up to a stated maximum, so a full match doubles a deposit under the ceiling and adds nothing above it.