The copy's size or price is different from the master's

Different lots come from your sizing rule. Small price differences come from brokers quoting different prices.

The lot size is different

That is usually what your settings asked for. Check the slave's Lot Sizing & Risk tab.

Fixed Multiplier: master lot times your multiplier.
Fixed Lot: always your fixed size.
Risk Percent: sized from the stop distance and your equity, so it changes with every trade.
Scale by Equity: master lot times your equity divided by the master's.

Also check:

Minimum and Maximum Allowed Lot, which cap the result.
Gold scale, which changes gold trades only.
A master trade without a stop loss on a Risk Percent slave. See When the master trade has no stop loss.
Futures: lots become whole contracts, so sizes are rounded. See Futures.

See Lot sizing for worked examples.

Each broker quotes its own price and spread, and the copy is placed a fraction of a second after the master. A small difference is normal.

Stops and targets are copied as a distance from entry, so the risk stays the same even when the entry differs.
Max Allowed Slippage sets how far the price may have moved for the copy to still be placed.

Profit differs with the lot size, the entry price, the broker's spread and commission, and the account's currency.

Reverse Copying is switched on for that slave. See Execution settings.