Do I need a client mod for timber?

No. Timber behavior is handled server-side. You connect with a normal client and follow whatever trigger the server uses, commonly an axe and sneak.

How is timber different from vein mining?

Timber targets trees and log stacks. Vein mining usually targets ores and mined blocks underground. Many servers avoid vein mining to keep mining progression slower while still removing the wood grind.

Can timber accidentally delete builds made of logs?

It can if the server lets placed logs chain-break. Safer configurations require sneaking, only affect naturally generated logs, or exclude player-placed blocks. If rules are unclear, test away from builds.

What are common balance limits on timber?

Extra durability loss, hunger cost, cooldowns, requiring an axe, and limiting it to natural logs are the usual controls. Some servers also disable it in certain worlds.

What kind of servers tend to run timber?

Survival and SMP communities that want less early-game busywork, plus build-heavy servers where gathering time is treated as overhead and projects are the main event.