Solutions offered are usually also valid regarding searching for a specific text in php-files or in SQL.
Although I also use Notepad++, I prefer using a file manager which has a lot of inbuilt utilities. (and it's Windows on my side, no Mac).
The one I use is not free , it's actually shareware (more precise nagware, forcing the user to press a designated button (1,2 or 3) at startup) but fully functional. In-built features are FTP, text search, fileviewer (including editor), file-compare, directory compare, archive viewer, USB installation (a necessity for me), quite a lot of plugins, very configurable, and lots more ...
Since it's strictly not free, I'm not going to name it but it should be easy to find using a search for file commanders in wikipedia. The name had to be changed many years ago due to Microsoft objecting to the use of "Windows" in it's name (in all honesty, Microsoft was very gracious in allowing a transition time and offering help and payment for a a new domainname and the transfer).
I've tried a couple of those softwares and most of them are similar in functionality but ease of use will depend on personal preference. I've stuck with one since around 1994 or 1995.
The bottom line is that there is no best solution, but many very good solutions, whether it's a dedicated program (which you'll need for very large files) or an (almost) all-in-one solution.
Spelling is freeware, which means you can use it for free.
On the other hand, it is not open source, which means you cannot change it or publish it in a modified form.