I recently got my first road/endurance bike, a Felt VR60. According to the specs, the wheels it came with are: Devox WheelRDS.A3, Tubeless ready, 6-hole, 12x100/12x142 mm. Default tires it came with are Vittoria Zaffira V tires.

I'm thinking of doing some light gravel riding with this bike, so was considering some 30mm tires to swap between depending on the activity I want to do. However, I have no idea what I should be looking for when it comes to buying new tires/tubes.

1. What factors do I need to worry about when buying new tires? I assume the wheel size matters, right?

2. Can I reuse my existing tubes, or do I need new ones?

3. Searching for 30mm gravel tires, I mostly found tubeless options. Is there a reason for that?

4. Anything else I should know before buying and swapping tires?

Any help is greatly appreciated here :)