Is the Mido Multifort Chronometer a good everyday watch?

Yes. The sapphire crystal, date window and steel bracelet make it easy to wear daily, and the automatic movement is certified for accuracy. It is dressy enough for the office and casual enough for weekends.

What does COSC chronometer certification mean here?

It means the movement was independently tested and passed strict accuracy limits across several positions and temperatures. In practice you get more consistent timekeeping than a standard uncertified Swiss automatic.

How does it compare with the Tissot Gentleman Powermatic 80?

Both are Swiss steel automatics with sapphire crystals. The Mido adds chronometer certification and a more distinctive case, while the Tissot is generally slimmer and more widely recognized.

Will the 42 mm case fit a small wrist?

It is on the larger side for a dress-sport watch. If your wrist is under about 6.5 inches, try it on first or compare the lug-to-lug measurement with a watch you already own.

Does it need winding if I don't wear it daily?

Yes. As an automatic, it winds from wrist movement, so it stops after a day or two off the wrist. Wear it regularly or use a watch winder to keep it running.