My interpretation of your post was that your arm is currently out of shape. Assuming that's accurate, then my opinion is you should get it in shape before starting up pitching. You don't want to start the season with a sore arm or in a deficit situation. So, yes, stick with long toss along with some other conditioning work to increase strength, flexibility, endurance, and stamina. Get yourself physically ready to carry the load and then put the load on the arm with pitching to dial in mechanics, accuracy, repeatability, etc.
Last year at the start of the season, the USC pitchers didn't touch a ball for 6 weeks. They spent those first 6 weeks doing conditioning work only. You don't have that much time so you need to start throwing in parallel with conditioning.
This is all just my opinion.