Three points:
1. A liner is more than enough... Bringing a sleeping bag on the Portuguese coastal route, in June is counter-productive, IMHO...
2. With the prevailing sea breezes, you will not feel hot or thirsty. Be CAREFUL. Dehydration can sneaky up on you. Try to drink at least .5 liters of non-alcoholic liquid per-hour walked. There are adequate cafes and shops along the route to obtain bottled water. I do not recall seeking fountains, but they are likely there.
I did this route, Porto to Santiago in early April 2015. The sky was cloudless and blue, the temperature was 27 (C), about 80 - 81 (F). I failed to drink enough as I did not FEEL thirsty. The result was three sudden onset episodes of syncope (fainting). My doctors in the US were livid when I returned home to a full and thorough cardiac workup. You do not want to KNOW how angry my wife was...
Prevention is better than the cure.
Other than this, the walk was wonderful. You will find the Portuguese people speak more and better English than their cousins in Spain. TV is subtitled in Portugal and not dubbed. Obtaining assistance was never a problem.
3. TIP #3 - One MUST STAY tip. Casa Fernanda! Fernanda and her husband operate an albergue out of their home. The sleeping facilities and showers are first-rate. They are in a cabin in the back garden / yard. The food is outstanding and there is plenty of it.
Fernanda is one of the many Camino Angels you will encounter. If you phone her before arriving, she will know how much food to obtain and prepare. Plus, you can reserve a bed in advance in this private albergue. Her number is +35. 191.458.9521. CALL BEFORE YOU LEAVE PORTO, or at least a day or two before you plan on arriving, so you know you have a bed. Both Fernanda and Jacinto speak fairly good English. Her fresh baked, homemade bread is "to die for..."
See this related posting:
https://www.caminodesantiago.me/community/threads/casa-de-fernanda.32535/
I hope this helps.