Yes, it is/will be the main drive. I have a second 1 TB HDD drive. Both internal.
For example, Crucial MX500
250 GB ~ ฿1,286.00,
500 GB ~ ฿2,415.00,
almost twice as expensive.
All my apps, including Windows, take appr. 100 GB on SSD. The rest goes to HDD.
I'm not sure how good Crucial MX500 is.