Managing storage is always a hassle. Even as storage grows, so does the size and number of files people want to keep. DaisyDisk is an excellent paid app for helping with this, and they do have a trial version so I recommend checking it out.
But macOS has a few search tricks built-in as well. Open a new Finder window then press Cmd F (or click Find in the File menu). The search bar appears in the window. If you click the first drop-down menu (mine is set to Kind), you’ll see a list of other criteria. Choose the last option in the menu: Other… There are well over 100 different criteria you can search on—so many that this window has its own search box! The one I’m interested in is File Size. Check it then click OK. Now you can search for files greater than say 20 MB.
Or say you want a view of all the recent files you’ve created or changed (useful for attaching files to email). Last modified date is within the last 2 weeks, and Kind is Document.
Whichever folder you are viewing before you choose Find, you can click the name of the folder—which is net the the This Mac option that is already selected—to narrow scope of the search to the current folder only.
Once you have the search criteria set how you want, click Save, name it, add it to the sidebar, and now you can use it just as you would any folder.
Tip: if you just want a list of every file on your computer, (which can be useful for doing a general audit, seeing where you might have duplicate files, etc.), you can do something clever like Created Date is before tomorrow (you’ll actually have to put the date of tomorrow in the search. Unfortunately I don’t know how to do relative dates in macOS)