btw, I'm not sure it fits what you are asking for, but I like Sombat's Thai. It's BYOB, no corkage fee. The owner mostly grows her herbs and the veggies are local grown. She is from Thailand. It only has 6-7 tables, so you need to reserve. No music, no bar, but it is a friendly place with a warm atmosphere, and Thai decor. Yes it is in a shopping center, which is kind of a two strip mall, next to Ken's. My family is addicted to their spicy fried rice.
In fact, Thai food is pretty much all I eat in Hilo. There are four or five Thai places, all good, none of them upscale, and all are patronized by residents.
Note: table service in Hilo is rarely polished, so don't expect it. Hilo Bay Cafe waitstaff think they are better than the average, but in my opinion they are worse, because they think they are better but they're not really any good at being properly attentive or in dealing with issues.
Cafe Pesto, which serves a lot of visitors due to its location, gets a bad rap for being all over the place with its food and sometimes it is just not very good. It does soup, salad, bread, and dessert very well. Haven't had its pizza in a long time. Has a full bar, with seating, although it would be loud seating facing the kitchen. Room has character, historic. Has real dining tables and chairs. (This is rare in Hilo.)
So on the face of it, Hilo Bay Cafe has them beat for their farm to table and all that, but service policy it doesn't. I quit going to Hilo Bay Cafe after they ruined one too many dishes and I had to argue with a snotty waitperson about whether or not they had screwed it up according to their definition. I've read other people with the same experience.
Last week I met a group for lunch who had decided on Cafe Pesto. I ordered something I won't identify that I didn't like at all. I thought about it thoroughly and decided it was really objectively bad and I told the server I was rejecting it. NO argument. I started to explain and she said, no need, if you don't like it you don't have to eat it, all you need to say. She took it off the bill and brought me something else, and I was happy.
At Hilo Bay Cafe they would have argued, resisted taking it off the bill, and punished me by bringing my substitute when the rest of the table was done. That's been my experience there. I hate that. I once had an organic greens salad there that was so natural it had real visible chunks of dirt in it. (That was before I knew that you can get rat lungworm disease from eating any local east side lettuce that isn't scrupulousy diligently washed, or I would have been horrified instead of merely annoyed.) They did take it away but they expressed no concern about the dirt. Cafe Pesto would have apologized profusely. So I like them better even though they are not for foodies. (But the desserts are fine.)
If you like sushi, Hilo is a good place for fresh sushi.
I think the problem with the "fresh local seafood" thing is that's a very American concept. Locals here aren't really into big pieces of fish as a main course. Seaside Restaurant does it, but it's not common. Locals love fish prepared in sushi, as sashimi, and as poke, and that's where the freshest fish is to be found, or smoked fish, not plated fish filets in a "seafood restaurant." They also love pig and chicken as much or more than fish.