Which restaurant should I have dinner at in Florence?

I’ve never heard of La Buchetta but all the others are good.
You will find the dishes you mention in any restaurant. If you find an Italian restaurant that doesn’t serve pasta, wine, and dessert, I’ll pay for your dinner. You might find restaurants that don’t serve meat only if you go to a vegan/vegetarian one.

Ristorante Pensavo Peggio

I have visited Florence many times and I have never made reservations. If the menu posted outside has pictures of their meals, or the menu posted is shown in 5 different languages, walk on by. You can always look on TripAdvisor for reviews.

All the places you've listed are solid. Florence is a great place for the sheer variety and number of restaurants to choose from. If there's a place I definitely want to go eat at, I go make reservations either via email if possible, having a hotel/BnB/host help out or, walk-in and ask. Also understand, some locations have seatings, this allows the kitchen to pace themselves and not be overwhelmed with a constant stream of orders. Places that do this will have a early (6 or 7pm) and a late seating (8 or 9pm)

I would like the food to be equally as nice as the atmosphere; something very comfortable and inviting, and not too "hole in the wall".

Keep in mind "restaurants" in Italy come in three varieties, most of them are the first two:

Osteria - generally this is a casual pub-grub kind of place. Very relaxed, zero formalities, service is simple and easy on the budget. Reservations can be made but walk-in's are usually the norm.

Trattoria - A bit more upscale than an Osteria but, still retaining rustic charm and familial atmosphere. Service can be more detailed, the menu may be more specialized or, focused but the overall feel is still relaxed and informal. Reservations are a good idea
Ristorante- This is a formal establishment, white table clothes, service is more pronounced, plate and flatware is unique, menu is much more refined and curated. Reservations are a must.

We had a great dinner at La Buchetta but we had to make reservations.

Osteria Cinghiale Bianco. An unforgettable eating experience. It's in the Otrarno. If I ever return to Florence, I will not leave without dining there.

Don't know how long you are staying. If you have the time, take the number 7 bus up into Fiesole.
La Reggia. Good food, nice view.