My doctor had me go to physical therapy from the beginning of all my treatments. I had 16 rounds of chemo and surgery before 30 radiation treatments. The ongoing PT helped with my range of motion. Radiation causes tightness for the rest of your life. Stretching is very important.
The radiation was not bad. I was very careful to use prescription steroid ointment and Aquaphor or calendula immediately after each treatment. Your skin must be clean and free of lotions beforehand. I would put the steroid on when getting dressed afterwards in the changing room. And use the Aquaphor and calendula throughout the day and before bed. I showered it off each morning before my treatment.

I walked my dogs almost every day. It helped with the fatigue from radiation. Staying active helped me. But I also took naps in the afternoon.

Good luck. I hope you have a good experience. Keep in mind that the most current radiation technology allows for shorter more precise radiation. It’s better than it was in the past.