Is it really necessary to keep ALL of your music, movies, tv shows and photos on your computer's internal drive? Think about that.....
A couple of years ago I made the decision to go with a MacBook Pro to replace my 21.5" iMac. Before I bought the new machine I spent some time reviewing all of my apps, folders and files and realized that I really did not need to keep some of the files and folders on my computer at all times. I went from a 1 TB "platter" drive in the iMac to a 512 SSD in the MacBook Pro. Before setting up the new machine I systematically went through the iMac again, this time with an external drive plugged into it, and copied the files and folders that I wanted to retain but didn't need in the computer itself. I also deleted old apps that I wasn't using any more. I then set up the new computer, this time using another external drive to copy over the files and folders that I wanted to keep on the MBP's internal SSD, dropping them into the appropriate categories on the drive. This makes for a lean, mean fast MacBook Pro that has an internal SSD that has plenty of room to breathe.
I continue to use external drives -- both for backup/archival purposes and for supplemental purposes. Platter drives work nicely for archiving and backing up one's computer and are less expensive. external SSDs are faster and significantly physically smaller, perfect for use at home as supplemental drives and also for taking along on the road when leaving the house. I want to retrieve a particular image from my photo files? Not a problem -- I just plug in one of the Samsung T5 external SSDs that I use for supplementing the computer's main SSD and grab the file or the image. External SSDs run in capacities of 250 GB, 500 GB, 1 TB and 2 TB and are a bit more expensive than "platter" drives of the same or larger capacities, but to me they are worth it in terms of speed and durability as well as portability.
Using external drives also has the advantage of making transfers from one machine to another very quick and convenient, plus when the time comes to set up another new computer, the process is streamlined. I have the 15" 2015 MBP and also a 2017 12" MacBook; some external hard drives today come with two cables, one with the "legacy" USB-A connector and one with a USB-C connector, so it's simply a matter of swapping out cables on the drives when doing something with two machines with different ports.
While it is possible to get an internal SSD up to 2 TB from Apple, this is usually a BTO (Built-to-Order) special order from the online Apple store, and it is quite expensive. Purchasing one or two external drives can be a more flexible way of keeping one's files available.