The best way to learn is by practicing, therefore, for anyone who wants to try BTC, it is a good idea to practice & understand through the testnet first.
No, it is not the recommended way don't make shit up. Bitcoin is hard to use already and learning about testnets, switching wallet configuration and whatnot will definitely lead to funds loss. All it takes is for the user to make a mistake once, confuse the testnet with the mainnet coins and send his real coins to somewhere where he can't recover it. Terrible advice.
Testnet is only for developers, always has been.
You are mixing things up. Bitcoin wallets isn't hard to use, I think they are the easiest without any complication, elelctrum is even the easiest of them. The only responsibility you have to take is to make sure your seed phrase is properly back up and that's it. You hardly see someone playing around testnet coins because they hold no value, they are mostly used for testing the network and maybe built some kind of applications or if the developer want to test one or two things.
Regarding confusion of sending Bitcoin from mainet to testnet, it's not possible. All Bitcoin testnet wallet start with some special characters to help differentiate between testnet and mainet wallet. Legacy wallet testnet start with m or n character while segwit start with t character. You either see something like this mhjdheuwond.... Or nkdqtbdnsk and segwit with tbq1..... or tbp1.... You can see that it's easy to spot t character in the testnet and absence of c character from the testnet, if you want to send Bitcoin to this address the wallet will say it's invalid.