Do cryptocurrency exchanges generally charge more for the exchange from FIAT money to Cryptocurrency than they do when
trading cryptocurrency for cryptocurrency?
Depends on the exchange, which exchange are we talking about here?
There will be fee deducted when you buy ALTs using BTC. The fee % varies among exchanges.
This comment is so vague it's not helpful.
There are two types of fees that you could incur.
(1) The fee charged by an exchange for the service they are providing; will be a set % of the transaction amount.
(2) The fee charged by miners to confirm a transaction on the blockchain; will be a variable nominal amount in Bitcoin that's set by the person initiating the exchange.
If you work with an exchange you'll pay both fees. The amount of each fee is totally dependent on the exchange you use.