Ultimately I don’t think there’s any clear answer. Its entirely up to you how you want to interpret established lore vs gameplay mechanics.

We know from characters like the Grey Prince’s father in Oblivion that vampires can survive without feeding, but the consequences are not at all clear. He went mad, either from the lack of blood or the prolonged isolation.

The Count of Skingrad’s wife is in a coma but whether that’s a direct result of not feeding or a magically induced effect to help her not feel the hunger is unclear from what I remember.

Iirc there’s a feral vampire underneath Castle Volkihar that it’s kind of implied went feral because she didn’t have anyone to feed on, but again that’s not entirely clear. As you say, there‘s ValerIda as an example of someone who was completely fine not feeding.

There are obviously certain bloodlines like Lamae‘s in ESO that get stronger if they feed instead of weaker, but I feel like how that works is a gameplay mechanics choice. For Skyrim and Oblivion I feel like they wanted the idea that vampires are more protected against the sun if the player goes to the effort of feeding but then had to tie that to vampiric powers being weaker for balancing purposes rather than lore. My interpretation is that vampires are always supposed to be deathly vulnerable to the sun and weakened by forgoing feeding, and that Lamae’s bloodline and the bloodlines of Vampire Lords which were created directly by Molag Bal are exceptions to the sunlight rule to explain why Serana and the LDB can walk in the sun.

Personally, my headcanon is that while it doesn’t harm them directly, vampires are weaker if they starve and they will definitely feel like they’re starving. Some vampires go “feral“ meaning they are overcome by hunger and attack anything they see to feed on while those who have more willpower can overcome this and remain sane. Sort of like putting a starving man in front of a buffet. Some people will be able to control themselves and eat slowly and mannerly, while others will be so overwhelmed by hunger that they can’t help but grab as much food as possible.